Storing an encoded data slice as a set of sub-slices

ABSTRACT

A method begins by storage units of a dispersed storage network (DSN) receiving a set of encoded data slices for storage. The method continues with a first storage unit determining whether to store a first encoded data slice as a first set of encoded data sub-slices. The method continues with the first storage unit encoding the first encoded data slice in accordance with a first dispersed storage error encoding function to produce the first set of encoded data sub-slices. The method continues by a second storage unit of the storage units determining whether to store a second encoded data slice as a second set of encoded data sub-slices. The method continues with the second storage unit encoding the second encoded data slice in accordance with a second dispersed storage error encoding function to produce the second set of encoded data sub-slices.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §120 as a continuation-in-part of U.S. Utility applicationSer. No. 14/275,560, entitled “LOCALIZED DISPERSED STORAGE MEMORYSYSTEM”, filed May 12, 2014, pending, which is a continuation of U.S.Utility application Ser. No. 13/779,452, entitled “LOCALIZED DISPERSEDSTORAGE MEMORY SYSTEM”, filed Feb. 27, 2013, now U.S. Pat. No.8,726,071, issued on May 13, 2014, which is a continuation of U.S.Utility application Ser. No. 12/845,590, entitled “LOCALIZED DISPERSEDSTORAGE MEMORY SYSTEM”, filed Jul. 28, 2010, now U.S. Pat. No.8,527,807, issued on Sep. 3, 2013, all of which are hereby incorporatedherein by reference in their entirety and made part of the present U.S.Utility Patent Application for all purposes.

U.S. Utility application Ser. No. 12/845,590 claims priority pursuant to35 USC §119(e) to U.S. Provisional Application No. 62/264,316, entitled“DISTRIBUTED STORAGE NETWORK MEMORY SYSTEM”, filed Nov. 25, 2009.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to computing systems and moreparticularly to data storage solutions within such computing systems.

Description of Related Art

Computers are known to communicate, process, and store data. Suchcomputers range from wireless smart phones to data centers that supportmillions of web searches, stock trades, or on-line purchases every day.In general, a computing system generates data and/or manipulates datafrom one form into another. For instance, an image sensor of thecomputing system generates raw picture data and, using an imagecompression program (e.g., JPEG, MPEG, etc.), the computing systemmanipulates the raw picture data into a standardized compressed image.

With continued advances in processing speed and communication speed,computers are capable of processing real time multimedia data forapplications ranging from simple voice communications to streaming highdefinition video. As such, general-purpose information appliances arereplacing purpose-built communications devices (e.g., a telephone). Forexample, smart phones can support telephony communications but they arealso capable of text messaging and accessing the internet to performfunctions including email, web browsing, remote applications access, andmedia communications (e.g., telephony voice, image transfer, musicfiles, video files, real time video streaming. etc.).

Each type of computer is constructed and operates in accordance with oneor more communication, processing, and storage standards. As a result ofstandardization and with advances in technology, more and moreinformation content is being converted into digital formats. Forexample, more digital cameras are now being sold than film cameras, thusproducing more digital pictures. As another example, web-basedprogramming is becoming an alternative to over the air televisionbroadcasts and/or cable broadcasts. As further examples, papers, books,video entertainment, home video, etc. are now being stored digitally,which increases the demand on the storage function of computers.

A typical computer storage system includes one or more memory devicesaligned with the needs of the various operational aspects of thecomputer's processing and communication functions. Generally, theimmediacy of access dictates what type of memory device is used. Forexample, random access memory (RAM) memory can be accessed in any randomorder with a constant response time, thus it is typically used for cachememory and main memory. By contrast, memory device technologies thatrequire physical movement such as magnetic disks, tapes, and opticaldiscs, have a variable response time as the physical movement can takelonger than the data transfer, thus they are typically used forsecondary memory (e.g., hard drive, backup memory, etc.).

A computer's storage system will be compliant with one or more computerstorage standards that include, but are not limited to, network filesystem (NFS), flash file system (FFS), disk file system (DFS), smallcomputer system interface (SCSI), internet small computer systeminterface (iSCSI), file transfer protocol (FTP), and web-baseddistributed authoring and versioning (WebDAV). These standards specifythe data storage format (e.g., files, data objects, data blocks,directories, etc.) and interfacing between the computer's processingfunction and its storage system, which is a primary function of thecomputer's memory controller.

Despite the standardization of the computer and its storage system,memory devices fail; especially commercial grade memory devices thatutilize technologies incorporating physical movement (e.g., a discdrive). For example, it is fairly common for a disc drive to routinelysuffer from bit level corruption and to completely fail after threeyears of use. One solution is to utilize a higher-grade disc drive,which adds significant cost to a computer.

Another solution is to utilize multiple levels of redundant disc drivesto replicate the data into two or more copies. One such redundant driveapproach is called redundant array of independent discs (RAID). In aRAID device, a RAID controller adds parity data to the original databefore storing it across the array. The parity data is calculated fromthe original data such that the failure of a disc will not result in theloss of the original data. For example, RAID 5 uses three discs toprotect data from the failure of a single disc. The parity data, andassociated redundancy overhead data, reduces the storage capacity ofthree independent discs by one third (e.g., n−1=capacity). RAID 6 canrecover from a loss of two discs and requires a minimum of four discswith a storage capacity of n−2.

While RAID addresses the memory device failure issue, it is not withoutits own failure issues that affect its effectiveness, efficiency andsecurity. For instance, as more discs are added to the array, theprobability of a disc failure increases, which increases the demand formaintenance. For example, when a disc fails, it needs to be manuallyreplaced before another disc fails and the data stored in the RAIDdevice is lost. To reduce the risk of data loss, data on a RAID deviceis typically copied on to one or more other RAID devices. While thisaddresses the loss of data issue, it raises a security issue sincemultiple copies of data are available, which increases the chances ofunauthorized access. Further, as the amount of data being stored grows,the overhead of RAID devices becomes a non-trivial efficiency issue.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a computingsystem in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an embodiment of a distributedstorage processing unit in accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of a grid module inaccordance with the present invention;

FIG. 5 is a diagram of an example embodiment of error coded data slicecreation in accordance with the present invention;

FIG. 6 is a schematic block diagram of an embodiment of a dispersedstorage unit in accordance with the present invention;

FIG. 7 is a schematic block diagram of another embodiment of a dispersedstorage unit in accordance with the present invention;

FIG. 8 is a flowchart illustrating an example of storing slices inaccordance with the present invention;

FIG. 9 is a flowchart illustrating an example of retrieving slices inaccordance with the present invention;

FIG. 10A is a flowchart illustrating an example of rebuilding memory inaccordance with the present invention;

FIG. 10B is a flowchart illustrating another example of rebuildingmemory in accordance with the present invention;

FIG. 11A is a schematic block diagram of another embodiment of adispersed storage unit in accordance with the present invention;

FIGS. 11B-D are schematic block diagrams of an embodiment of a dispersedstorage network in accordance with the present invention;

FIG. 11E is a flowchart illustrating another example of storing slicesin accordance with the present invention;

FIG. 12 is another flowchart illustrating another example of storingslices in accordance with the present invention;

FIG. 13 is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 14 is a flowchart illustrating an example of distributing slices inaccordance with the present invention;

FIG. 15A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 15B is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 16A is a flowchart illustrating an example of determining memoryutilization in accordance with present invention; and

FIG. 16B is a flowchart illustrating another example of determiningmemory utilization in accordance with present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a computing system 10 thatincludes one or more of a first type of user devices 12, one or more ofa second type of user devices 14, at least one distributed storage (DS)processing unit 16, at least one DS managing unit 18, at least onestorage integrity processing unit 20, and a distributed storage network(DSN) memory 22 coupled via a network 24. The network 24 may include oneor more wireless and/or wire lined communication systems; one or moreprivate intranet systems and/or public internet systems; and/or one ormore local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of distributed storage (DS) units36 for storing data of the system. Each of the DS units 36 includes aprocessing module and memory and may be located at a geographicallydifferent site than the other DS units (e.g., one in Chicago, one inMilwaukee, etc.). The processing module may be a single processingdevice or a plurality of processing devices. Such a processing devicemay be a microprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module may have an associatedmemory and/or memory element, which may be a single memory device, aplurality of memory devices, and/or embedded circuitry of the processingmodule. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module includes morethan one processing device, the processing devices may be centrallylocated (e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that when the processing module implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory and/or memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Still further notethat, the memory element stores, and the processing module executes,hard coded and/or operational instructions corresponding to at leastsome of the steps and/or functions illustrated in FIGS. 1-16.

Each of the user devices 12-14, the DS processing unit 16, the DSmanaging unit 18, and the storage integrity processing unit 20 may be aportable computing device (e.g., a social networking device, a gamingdevice, a cell phone, a smart phone, a personal digital assistant, adigital music player, a digital video player, a laptop computer, ahandheld computer, a video game controller, and/or any other portabledevice that includes a computing core) and/or a fixed computing device(e.g., a personal computer, a computer server, a cable set-top box, asatellite receiver, a television set, a printer, a fax machine, homeentertainment equipment, a video game console, and/or any type of homeor office computing equipment). Such a portable or fixed computingdevice includes a computing core 26 and one or more interfaces 30, 32,and/or 33. An embodiment of the computing core 26 will be described withreference to FIG. 2.

With respect to the interfaces, each of the interfaces 30, 32, and 33includes software and/or hardware to support one or more communicationlinks via the network 24 and/or directly. For example, interface 30supports a communication link (wired, wireless, direct, via a LAN, viathe network 24, etc.) between the first type of user device 14 and theDS processing unit 16. As another example, DSN interface 32 supports aplurality of communication links via the network 24 between the DSNmemory 22 and the DS processing unit 16, the first type of user device12, and/or the storage integrity processing unit 20. As yet anotherexample, interface 33 supports a communication link between the DSmanaging unit 18 and any one of the other devices and/or units 12, 14,16, 20, and/or 22 via the network 24.

In general and with respect to data storage, the system 10 supportsthree primary functions: distributed network data storage management,distributed data storage and retrieval, and data storage integrityverification. In accordance with these three primary functions, data canbe distributedly stored in a plurality of physically different locationsand subsequently retrieved in a reliable and secure manner regardless offailures of individual storage devices, failures of network equipment,the duration of storage, the amount of data being stored, attempts athacking the data, etc.

The DS managing unit 18 performs distributed network data storagemanagement functions, which include establishing distributed datastorage parameters, performing network operations, performing networkadministration, and/or performing network maintenance. The DS managingunit 18 establishes the distributed data storage parameters (e.g.,allocation of virtual DSN memory space, distributed storage parameters,security parameters, billing information, user profile information,etc.) for one or more of the user devices 12-14 (e.g., established forindividual devices, established for a user group of devices, establishedfor public access by the user devices, etc.). For example, the DSmanaging unit 18 coordinates the creation of a vault (e.g., a virtualmemory block) within the DSN memory 22 for a user device (for a group ofdevices, or for public access). The DS managing unit 18 also determinesthe distributed data storage parameters for the vault. In particular,the DS managing unit 18 determines a number of slices (e.g., the numberthat a data segment of a data file and/or data block is partitioned intofor distributed storage) and a read threshold value (e.g., the minimumnumber of slices required to reconstruct the data segment).

As another example, the DS managing unit 18 creates and stores, locallyor within the DSN memory 22, user profile information. The user profileinformation includes one or more of authentication information,permissions, and/or the security parameters. The security parameters mayinclude one or more of encryption/decryption scheme, one or moreencryption keys, key generation scheme, and data encoding/decodingscheme.

As yet another example, the DS managing unit 18 creates billinginformation for a particular user, user group, vault access, publicvault access, etc. For instance, the DS managing unit 18 tracks thenumber of times a user accesses a private vault and/or public vaults,which can be used to generate a per-access bill. In another instance,the DS managing unit 18 tracks the amount of data stored and/orretrieved by a user device and/or a user group, which can be used togenerate a per-data-amount bill.

The DS managing unit 18 also performs network operations, networkadministration, and/or network maintenance. As at least part ofperforming the network operations and/or administration, the DS managingunit 18 monitors performance of the devices and/or units of the system10 for potential failures, determines the devices' and/or units'activation status, determines the devices' and/or units' loading, andany other system level operation that affects the performance level ofthe system 10. For example, the DS managing unit 18 receives andaggregates network management alarms, alerts, errors, statusinformation, performance information, and messages from the devices12-14 and/or the units 16, 20, 22. For example, the DS managing unit 18receives a simple network management protocol (SNMP) message regardingthe status of the DS processing unit 16.

The DS managing unit 18 performs the network maintenance by identifyingequipment within the system 10 that needs replacing, upgrading,repairing, and/or expanding. For example, the DS managing unit 18determines that the DSN memory 22 needs more DS units 36 or that one ormore of the DS units 36 needs updating.

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has a data file 38 and/or data block 40 tostore in the DSN memory 22, it sends the data file 38 and/or data block40 to the DS processing unit 16 via its interface 30. As will bedescribed in greater detail with reference to FIG. 2, the interface 30functions to mimic a conventional operating system (OS) file systeminterface (e.g., network file system (NFS), flash file system (FFS),disk file system (DFS), file transfer protocol (FTP), web-baseddistributed authoring and versioning (WebDAV), etc.) and/or a blockmemory interface (e.g., small computer system interface (SCSI), internetsmall computer system interface (iSCSI), etc.). In addition, theinterface 30 may attach a user identification code (ID) to the data file38 and/or data block 40.

The DS processing unit 16 receives the data file 38 and/or data block 40via its interface 30 and performs a distributed storage (DS) process 34thereon (e.g., an error coding dispersal storage function). The DSprocessing 34 begins by partitioning the data file 38 and/or data block40 into one or more data segments, which is represented as Y datasegments. For example, the DS processing 34 may partition the data file38 and/or data block 40 into a fixed byte size segment (e.g., 2¹ to2^(n) bytes, where n=>2) or a variable byte size (e.g., change byte sizefrom segment to segment, or from groups of segments to groups ofsegments, etc.).

For each of the Y data segments, the DS processing 34 error encodes(e.g., forward error correction (FEC), information dispersal algorithm,or error correction coding) and slices (or slices then error encodes)the data segment into a plurality of error coded (EC) data slices 42-48,which is represented as X slices per data segment. The number of slices(X) per segment, which corresponds to a number of pillars n, is set inaccordance with the distributed data storage parameters and the errorcoding scheme. For example, if a Reed-Solomon (or other FEC scheme) isused in an n/k system, then a data segment is divided into n slices,where k number of slices is needed to reconstruct the original data(i.e., k is the threshold). As a few specific examples, the n/k factormay be 5/3; 6/4; 8/6; 8/5; 16/10.

For each EC slice 42-48, the DS processing unit 16 creates a uniqueslice name and appends it to the corresponding EC slice 42-48. The slicename includes universal DSN memory addressing routing information (e.g.,virtual memory addresses in the DSN memory 22) and user-specificinformation (e.g., user ID, file name, data block identifier, etc.).

The DS processing unit 16 transmits the plurality of EC slices 42-48 toa plurality of DS units 36 of the DSN memory 22 via the DSN interface 32and the network 24. The DSN interface 32 formats each of the slices fortransmission via the network 24. For example, the DSN interface 32 mayutilize an internet protocol (e.g., TCP/IP, etc.) to packetize the ECslices 42-48 for transmission via the network 24.

The number of DS units 36 receiving the EC slices 42-48 is dependent onthe distributed data storage parameters established by the DS managingunit 18. For example, the DS managing unit 18 may indicate that eachslice is to be stored in a different DS unit 36. As another example, theDS managing unit 18 may indicate that like slice numbers of differentdata segments are to be stored in the same DS unit 36. For example, thefirst slice of each of the data segments is to be stored in a first DSunit 36, the second slice of each of the data segments is to be storedin a second DS unit 36, etc. In this manner, the data is encoded anddistributedly stored at physically diverse locations to improve datastorage integrity and security. Further examples of encoding the datasegments will be provided with reference to one or more of FIGS. 2-16.

Each DS unit 36 that receives an EC slice 42-48 for storage translatesthe virtual DSN memory address of the slice into a local physicaladdress for storage. Accordingly, each DS unit 36 maintains a virtual tophysical memory mapping to assist in the storage and retrieval of data.

The first type of user device 12 performs a similar function to storedata in the DSN memory 22 with the exception that it includes the DSprocessing. As such, the device 12 encodes and slices the data fileand/or data block it has to store. The device then transmits the slices11 to the DSN memory via its DSN interface 32 and the network 24.

For a second type of user device 14 to retrieve a data file or datablock from memory, it issues a read command via its interface 30 to theDS processing unit 16. The DS processing unit 16 performs the DSprocessing 34 to identify the DS units 36 storing the slices of the datafile and/or data block based on the read command. The DS processing unit16 may also communicate with the DS managing unit 18 to verify that theuser device 14 is authorized to access the requested data.

Assuming that the user device is authorized to access the requesteddata, the DS processing unit 16 issues slice read commands to at least athreshold number of the DS units 36 storing the requested data (e.g., toat least 10 DS units for a 16/10 error coding scheme). Each of the DSunits 36 receiving the slice read command, verifies the command,accesses its virtual to physical memory mapping, retrieves the requestedslice, or slices, and transmits it to the DS processing unit 16.

Once the DS processing unit 16 has received a read threshold number ofslices for a data segment, it performs an error decoding function andde-slicing to reconstruct the data segment. When Y number of datasegments has been reconstructed, the DS processing unit 16 provides thedata file 38 and/or data block 40 to the user device 14. Note that thefirst type of user device 12 performs a similar process to retrieve adata file and/or data block.

The storage integrity processing unit 20 performs the third primaryfunction of data storage integrity verification. In general, the storageintegrity processing unit 20 periodically retrieves slices 45, and/orslice names, of a data file or data block of a user device to verifythat one or more slices have not been corrupted or lost (e.g., the DSunit failed). The retrieval process mimics the read process previouslydescribed.

If the storage integrity processing unit 20 determines that one or moreslices is corrupted or lost, it rebuilds the corrupted or lost slice(s)in accordance with the error coding scheme. The storage integrityprocessing unit 20 stores the rebuilt slice, or slices, in theappropriate DS unit(s) 36 in a manner that mimics the write processpreviously described.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface 60, at least one IO device interface module 62, a readonly memory (ROM) basic input output system (BIOS) 64, and one or morememory interface modules. The memory interface module(s) includes one ormore of a universal serial bus (USB) interface module 66, a host busadapter (HBA) interface module 68, a network interface module 70, aflash interface module 72, a hard drive interface module 74, and a DSNinterface module 76. Note the DSN interface module 76 and/or the networkinterface module 70 may function as the interface 30 of the user device14 of FIG. 1. Further note that the TO device interface module 62 and/orthe memory interface modules may be collectively or individuallyreferred to as TO ports.

The processing module 50 may be a single processing device or aplurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module 50 may have anassociated memory and/or memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry of theprocessing module 50. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module 50includes more than one processing device, the processing devices may becentrally located (e.g., directly coupled together via a wired and/orwireless bus structure) or may be distributedly located (e.g., cloudcomputing via indirect coupling via a local area network and/or a widearea network). Further note that when the processing module 50implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory and/ormemory element storing the corresponding operational instructions may beembedded within, or external to, the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.Still further note that, the memory element stores, and the processingmodule 50 executes, hard coded and/or operational instructionscorresponding to at least some of the steps and/or functions illustratedin FIGS. 1-16.

FIG. 3 is a schematic block diagram of an embodiment of a dispersedstorage (DS) processing module 34 of user device 12 and/or of the DSprocessing unit 16. The DS processing module 34 includes a gatewaymodule 78, an access module 80, a grid module 82, and a storage module84. The DS processing module 34 may also include an interface 30 and theDSnet interface 32 or the interfaces 68 and/or 70 may be part of userdevice 12 or of the DS processing unit 16. The DS processing module 34may further include a bypass/feedback path between the storage module 84to the gateway module 78. Note that the modules 78-84 of the DSprocessing module 34 may be in a single unit or distributed acrossmultiple units.

In an example of storing data, the gateway module 78 receives anincoming data object that includes a user ID field 86, an object namefield 88, and the data object field 40 and may also receivecorresponding information that includes a process identifier (e.g., aninternal process/application ID), metadata, a file system directory, ablock number, a transaction message, a user device identity (ID), a dataobject identifier, a source name, and/or user information. The gatewaymodule 78 authenticates the user associated with the data object byverifying the user ID 86 with the DS managing unit 18 and/or anotherauthenticating unit.

When the user is authenticated, the gateway module 78 obtains userinformation from the management unit 18, the user device, and/or theother authenticating unit. The user information includes a vaultidentifier, operational parameters, and user attributes (e.g., userdata, billing information, etc.). A vault identifier identifies a vault,which is a virtual memory space that maps to a set of DS storage units36. For example, vault 1 (i.e., user 1's DSN memory space) includeseight DS storage units (X=8 wide) and vault 2 (i.e., user 2's DSN memoryspace) includes sixteen DS storage units (X=16 wide). The operationalparameters may include an error coding algorithm, the width n (number ofpillars X or slices per segment for this vault), a read threshold T, awrite threshold, an encryption algorithm, a slicing parameter, acompression algorithm, an integrity check method, caching settings,parallelism settings, and/or other parameters that may be used to accessthe DSN memory layer.

The gateway module 78 uses the user information to assign a source name35 to the data. For instance, the gateway module 78 determines thesource name 35 of the data object 40 based on the vault identifier andthe data object. For example, the source name may contain a fileidentifier (ID), a vault generation number, a reserved field, and avault identifier (ID). As another example, the gateway module 78 maygenerate the file ID based on a hash function of the data object 40.Note that the gateway module 78 may also perform message conversion,protocol conversion, electrical conversion, optical conversion, accesscontrol, user identification, user information retrieval, trafficmonitoring, statistics generation, configuration, management, and/orsource name determination.

The access module 80 receives the data object 40 and creates a series ofdata segments 1 through Y 90-92 in accordance with a data storageprotocol (e.g., file storage system, a block storage system, and/or anaggregated block storage system). The number of segments Y may be chosenor randomly assigned based on a selected segment size and the size ofthe data object. For example, if the number of segments is chosen to bea fixed number, then the size of the segments varies as a function ofthe size of the data object. For instance, if the data object is animage file of 4,194,304 eight bit bytes (e.g., 33,554,432 bits) and thenumber of segments Y=131,072, then each segment is 256 bits or 32 bytes.As another example, if segment size is fixed, then the number ofsegments Y varies based on the size of data object. For instance, if thedata object is an image file of 4,194,304 bytes and the fixed size ofeach segment is 4,096 bytes, then the number of segments Y=1,024. Notethat each segment is associated with the same source name.

The grid module 82 receives the data segments and may manipulate (e.g.,compression, encryption, cyclic redundancy check (CRC), etc.) each ofthe data segments before performing an error coding function of theerror coding dispersal storage function to produce a pre-manipulateddata segment. After manipulating a data segment, if applicable, the gridmodule 82 error encodes (e.g., Reed-Solomon, Convolution encoding,Trellis encoding, etc.) the data segment or manipulated data segmentinto X error coded data slices 42-44.

The value X, or the number of pillars (e.g., X=16), is chosen as aparameter of the error coding dispersal storage function. Otherparameters of the error coding dispersal function include a readthreshold T, a write threshold W, etc. The read threshold (e.g., T=10,when X=16) corresponds to the minimum number of error-free error codeddata slices required to reconstruct the data segment. In other words,the DS processing module 34 can compensate for X−T (e.g., 16−10=6)missing error coded data slices per data segment. The write threshold Wcorresponds to a minimum number of DS storage units that acknowledgeproper storage of their respective data slices before the DS processingmodule indicates proper storage of the encoded data segment. Note thatthe write threshold is greater than or equal to the read threshold for agiven number of pillars (X).

For each data slice of a data segment, the grid module 82 generates aunique slice name 37 and attaches it thereto. The slice name 37 includesa universal routing information field and a vault specific field and maybe 48 bytes (e.g., 24 bytes for each of the universal routinginformation field and the vault specific field). As illustrated, theuniversal routing information field includes a slice index, a vault ID,a vault generation, and a reserved field. The slice index is based onthe pillar number and the vault ID and, as such, is unique for eachpillar (e.g., slices of the same pillar for the same vault for anysegment will share the same slice index). The vault specific fieldincludes a data name, which includes a file ID and a segment number(e.g., a sequential numbering of data segments 1-Y of a simple dataobject or a data block number).

Prior to outputting the error coded data slices of a data segment, thegrid module may perform post-slice manipulation on the slices. Ifenabled, the manipulation includes slice level compression, encryption,CRC, addressing, tagging, and/or other manipulation to improve theeffectiveness of the computing system.

When the error coded data slices of a data segment are ready to beoutputted, the grid module 82 determines which of the DS storage units36 will store the EC data slices based on a dispersed storage memorymapping associated with the user's vault and/or DS storage unitattributes. The DS storage unit attributes may include availability,self-selection, performance history, link speed, link latency,ownership, available DSN memory, domain, cost, a prioritization scheme,a centralized selection message from another source, a lookup table,data ownership, and/or any other factor to optimize the operation of thecomputing system. Note that the number of DS storage units 36 is equalto or greater than the number of pillars (e.g., X) so that no more thanone error coded data slice of the same data segment is stored on thesame DS storage unit 36. Further note that EC data slices of the samepillar number but of different segments (e.g., EC data slice 1 of datasegment 1 and EC data slice 1 of data segment 2) may be stored on thesame or different DS storage units 36.

The storage module 84 performs an integrity check on the outboundencoded data slices and, when successful, identifies a plurality of DSstorage units based on information provided by the grid module 82. Thestorage module 84 then outputs the encoded data slices 1 through X ofeach segment 1 through Y to the DS storage units 36. Each of the DSstorage units 36 stores its EC data slice(s) and maintains a localvirtual DSN address to physical location table to convert the virtualDSN address of the EC data slice(s) into physical storage addresses.

In an example of a read operation, the user device 12 and/or 14 sends aread request to the DS processing unit 16, which authenticates therequest. When the request is authentic, the DS processing unit 16 sendsa read message to each of the DS storage units 36 storing slices of thedata object being read. The slices are received via the DSnet interface32 and processed by the storage module 84, which performs a parity checkand provides the slices to the grid module 82 when the parity check wassuccessful. The grid module 82 decodes the slices in accordance with theerror coding dispersal storage function to reconstruct the data segment.The access module 80 reconstructs the data object from the data segmentsand the gateway module 78 formats the data object for transmission tothe user device.

FIG. 4 is a schematic block diagram of an embodiment of a grid module 82that includes a control unit 73, a pre-slice manipulator 75, an encoder77, a slicer 79, a post-slice manipulator 81, a pre-slice de-manipulator83, a decoder 85, a de-slicer 87, and/or a post-slice de-manipulator 89.Note that the control unit 73 may be partially or completely external tothe grid module 82. For example, the control unit 73 may be part of thecomputing core at a remote location, part of a user device, part of theDS managing unit 18, or distributed amongst one or more DS storageunits.

In an example of a write operation, the pre-slice manipulator 75receives a data segment 90-92 and a write instruction from an authorizeduser device. The pre-slice manipulator 75 determines if pre-manipulationof the data segment 90-92 is required and, if so, what type. Thepre-slice manipulator 75 may make the determination independently orbased on instructions from the control unit 73, where the determinationis based on a computing system-wide predetermination, a table lookup,vault parameters associated with the user identification, the type ofdata, security requirements, available DSN memory, performancerequirements, and/or other metadata.

Once a positive determination is made, the pre-slice manipulator 75manipulates the data segment 90-92 in accordance with the type ofmanipulation. For example, the type of manipulation may be compression(e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.),signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA,Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g.,Data Encryption Standard, Advanced Encryption Standard, etc.), addingmetadata (e.g., time/date stamping, user information, file type, etc.),cyclic redundancy check (e.g., CRC32), and/or other data manipulationsto produce the pre-manipulated data segment.

The encoder 77 encodes the pre-manipulated data segment 92 using aforward error correction (FEC) encoder (and/or other type of erasurecoding and/or error coding) to produce an encoded data segment 94. Theencoder 77 determines which forward error correction algorithm to usebased on a predetermination associated with the user's vault, a timebased algorithm, user direction, DS managing unit direction, controlunit direction, as a function of the data type, as a function of thedata segment 92 metadata, and/or any other factor to determine algorithmtype. The forward error correction algorithm may be Golay,Multidimensional parity, Reed-Solomon, Hamming, Bose Ray ChauduriHocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Notethat the encoder 77 may use a different encoding algorithm for each datasegment 92, the same encoding algorithm for the data segments 92 of adata object, or a combination thereof.

The encoded data segment 94 is of greater size than the data segment 92by the overhead rate of the encoding algorithm by a factor of X/T, whereX is the width or number of slices, and T is the read threshold. In thisregard, the corresponding decoding process can accommodate at most X−Tmissing EC data slices and still recreate the data segment 92. Forexample, if X=16 and T=10, then the data segment 92 will be recoverableas long as 10 or more EC data slices per segment are not corrupted.

The slicer 79 transforms the encoded data segment 94 into EC data slicesin accordance with the slicing parameter from the vault for this userand/or data segment 92. For example, if the slicing parameter is X=16,then the slicer 79 slices each encoded data segment 94 into 16 encodedslices.

The post-slice manipulator 81 performs, if enabled, post-manipulation onthe encoded slices to produce the EC data slices. If enabled, thepost-slice manipulator 81 determines the type of post-manipulation,which may be based on a computing system-wide predetermination,parameters in the vault for this user, a table lookup, the useridentification, the type of data, security requirements, available DSNmemory, performance requirements, control unit directed, and/or othermetadata. Note that the type of post-slice manipulation may includeslice level compression, signatures, encryption, CRC, addressing,watermarking, tagging, adding metadata, and/or other manipulation toimprove the effectiveness of the computing system.

In an example of a read operation, the post-slice de-manipulator 89receives at least a read threshold number of EC data slices and performsthe inverse function of the post-slice manipulator 81 to produce aplurality of encoded slices. The de-slicer 87 de-slices the encodedslices to produce an encoded data segment 94. The decoder 85 performsthe inverse function of the encoder 77 to recapture the data segment90-92. The pre-slice de-manipulator 83 performs the inverse function ofthe pre-slice manipulator 75 to recapture the data segment 90-92.

FIG. 5 is a diagram of an example of slicing an encoded data segment 94by the slicer 79. In this example, the encoded data segment 94 includesthirty-two bits, but may include more or less bits. The slicer 79disperses the bits of the encoded data segment 94 across the EC dataslices in a pattern as shown. As such, each EC data slice does notinclude consecutive bits of the data segment 94 reducing the impact ofconsecutive bit failures on data recovery. For example, if EC data slice2 (which includes bits 1, 5, 9, 13, 17, 25, and 29) is unavailable(e.g., lost, inaccessible, or corrupted), the data segment can bereconstructed from the other EC data slices (e.g., 1, 3 and 4 for a readthreshold of 3 and a width of 4).

FIG. 6 is a schematic block diagram of an embodiment of a dispersedstorage (DS) unit. As illustrated, the DS unit 102 includes a storageunit control module 104, a plurality of memories of type A (1 througha), and a plurality of memories of type B (1 through b). The storageunit control module 104 may be implemented with the computing core 26.The memories may be one or more of a magnetic hard disk, NAND flash,read only memory, optical disk, and any other type of read-only orread/write memory. The memories may be implemented as part of or outsideof the DS unit 102. For example, memory A-1 may be implemented in the DSunit 102 and memory A-2 may be implemented in a remote server (e.g., adifferent DS unit operably coupled to the DS unit 102 via the network).In an example, memory A-1 through memory A-a are implemented with themagnetic hard disk technology and memory B-1 through memory B-b areimplemented with the NAND flash technology.

As illustrated, the storage unit control module 104 includes the DSnetinterface 32, a DS tables and logs memory 106, an operating system (OS)memory 108, and the DS processing 34. The storage unit control module104 may be operably coupled to the computing system 10 via the DSnetinterface 32 by way of the network 24. The storage unit control module104 receives a store command, metadata, and data to store via the DSnetinterface 32. The data may include a simple object file, a block file,and/or error coded data slices. In response, the DS processing 34 of thestorage unit control module 104 stores data in memory A and/or memory B.In an example, the DS processing 34 stores the data in the memory Aand/or memory B substantially as received (e.g., a data slice is storedas a slice, a block file is stored as a block file, etc.).

In another example, the DS processing 34 encodes a portion of the datain accordance with an error coded dispersal storage function to produceencoded data slices, determines where to store the encoded data slices,and stores the encoded data slices in the memory A and/or memory B. Sucha determination may be based on one or more of the metadata, a command(e.g., from a DS processing unit 16 indicating which memory type touse), a type of data indicator, a local virtual DSN address to physicallocation table lookup, a priority indicator, a security indicator,available memory, memory performance data, memory status, memory costdata, and/or any other parameter to facilitate desired levels ofefficiency and performance. For example, the storage unit control module104 may choose memory A-1 (e.g., a magnetic hard disk drive) to store areceived data slice since the performance and efficiency is good enoughfor the data slice requirements (e.g., availability, cost, responsetime). In an instance, the DS processing 34 stores the data slices atvarious addresses across memory A-1. In another instance, the DSprocessing 34 stores the data slices across more than one of DS unit 102memories. In another instance, the DS processing 34 stores a threshold knumber of the data slices across memory B (for fast retrieval) and theother slicing pillar with minus the threshold number (n−k) updatedslices across memory A. In another instance, the DS processing 34 storesthe data slices across the DS unit 102 memories and at least one otherDS unit at the same site as the DS unit 102. In another instance, the DSprocessing 34 stores the data slices across the DS unit 102 memories andat least one other DS unit at a different site as the DS unit 102. Themethod to store and retrieve data slices will be discussed in greaterdetail with reference to FIGS. 7-9.

The storage unit control module 104 creates and maintains the localvirtual DSN address to physical memory table as part of the DS tables106. The storage unit control module 104 determines where previouslystored data slices are located based on the local virtual DSN address tophysical memory table. The storage unit control module 104 savesactivity records (e.g., memory utilization, errors, stores, retrievals,etc.) as the logs in the DS tables and logs memory 106.

The storage unit control module 104 utilizes the DS processing 34 todistributedly store information from the DS tables and logs 106 and theoperating system memory 108 as data slices in memory A and/or memory Bto improve the reliability of operation of the DS unit 102. The storageunit control module 104 determines when to distributedly store one ormore of the DS tables and logs 106 and the OS memory 108. Such adetermination may be based on one or more of a time period has expiredsince the last store, a command, an error message, a change in thememory architecture (e.g., a new memory device is added), and at leastone of the DS tables and logs 106 and OS memory 108 have changed sincethe last store. The storage unit control module 104 determines where todistributedly store data slices of DS tables and logs 106 and OS memory108 when the storage unit control module 104 determines to distributedlystore the data slices. Such a determination may be based on one or moreof a predetermination, a command, a management configuration parameter,a reliability indicator, a memory status indicator, a performancehistory indicator, DSN memory architecture, and any other factor tooptimize the system reliability.

FIG. 7 is a schematic block diagram of another embodiment of a dispersedstorage (DS) unit. As illustrated, the DS unit includes a DS processing34 and a memory A-1. In an example, memory A-1 has one billion bytes ofstorage capacity. In an example of a storage operation, the DSprocessing 34 receives 900 bytes of data 109. The DS processing 34determines an error coded dispersal storage function with a pillar widthn=4 and a read threshold=3. The DS processing 34 encodes the data 109 inaccordance with the error coded dispersal storage function to producefour data slices (e.g., of the four pillars) where the data slices areeach approximately 300 bytes in size. The DS processing 34 determinesaddressable locations within memory A-1 to store the data slices basedon one or more of a lookup of where the last slices were stored, thelocal virtual DSN address to physical location table, available memory,memory status, a command, memory errors, and the error coded dispersalstorage function. In an instance, the DS processing 34 determines toevenly space the pillars apart evenly across the memory A-1 (e.g.,spaced apart by 250 megabytes across the 1 gigabyte memory). In anotherinstance, the DS processing 34 determines to utilize memory addressesthat avoid known issues as indicated by the memory status for memory A-1(e.g., 400 megabytes between pillars 1 and 2 to avoid an issue ataddress 300 million, 100 megabytes between pillars 2 and 3, and 150megabytes between pillars 3 and 4). Next, the DS processing 34 storesthe data slices in the memory A-1 at the addressable locations.

In an example of a re-commissioning operation, a hard disk drive isutilized for a first time period (e.g., three years) within anon-dispersed storage system (e.g., a RAID system). The hard disk driveis re-commissioned in a dispersed storage system at the end of the firsttime or when a number of disk drive errors exceeds an error threshold.For example, the hard disk drive is removed from the non-dispersedstorage system and installed in the dispersed storage system when thehard disk drive is producing too many disk drive errors. A processingmodule of the DS processing module 34 generates an initial error profile(e.g., reliability of the hard disk drive by addressable storagesectors) and determines a dispersal configuration (including a memoryutilization approach) based on the initial error profile. The processingmodule generates the initial error profile by the generating test data,storing the test data in two or more storage sectors of a set ofaddressable storage sectors, retrieving the test data from the two ormore storage sectors of the set of addressable storage sectors toproduce retrieved test data.

Next, the processing module compares the retrieved test data to the testdata. The processing module determines that a storage error has beendetected when the comparison is unfavorable (e.g., when substantiallydifferent). The processing module determines that a storage error hasnot been detected when the comparison is favorable (e.g., whensubstantially the same). The processing module produces the initialerror profile by listing the detected storage errors and thecorresponding addressable storage sectors. The processing moduledetermines the dispersal configuration based on the initial errorprofile to avoid using addressable storage sectors corresponding todetected storage errors. Note that as the hard disk drive is utilized inthe dispersed storage system, the processing module produces an errorprofile when storage errors are detected and rebuilds stored data withinthe hard disk drive in accordance with the error profile. The method ofoperation to rebuild data is discussed below. The method of operation tostore data is discussed with reference to FIG. 8. Note that theeffective lifespan of the hard disk drive may be extended by utilizingthe hard disk drive in the dispersed storage system where overall datareliability is above acceptable levels even though individual hard diskdrives may produce errors above unacceptable levels in a non-dispersedstorage system.

In an example of a rebuilding operation of a single hard drive, aprocessing module detects a storage error of an encoded data slice(e.g., an integrity test failure, a checksum test failure, a missingdata slice indicator, etc.) of a set of encoded data slices, wherein theset of encoded data slices represents data encoded using an error codingdispersal storage function, wherein the single hard drive is defined tohave a set of addressable storage sectors, and wherein encoded dataslices of the set of encoded data slices are stored in correspondingaddressable storage sectors of the set of addressable storage sectors.In addition, the processing module may detect a plurality of storageerrors and determine a rate of increase of the plurality of storageerrors. Next, the processing module evaluates the rate of increase ofthe plurality of storage errors to determine a level of reliability. Theprocessing module determines a second error type when a size of usablestorage space is greater than a storage threshold and when the level ofreliability compares unfavorably to a reliability threshold.

Alternatively, or in addition to, the processing module detects astorage error of an encoded data slice of a plurality of sets of encodeddata slices, wherein the plurality of sets of encoded data slicesrepresents a plurality of data segments each encoded using the errorcoding dispersal storage function, wherein a first encoded data slice ofeach of the plurality of sets of encoded data slices is stored in afirst addressable storage sector of the set of addressable storagesectors, and wherein a second encoded data slice of each of theplurality of sets of encoded data slices is stored in a secondaddressable storage sector of the set of addressable storage sectors.

The method of the rebuilding example continues where the processingmodule updates an error profile based on the storage error(s). Theprocessing module determines a type of error for the storage error. Sucha determination of the type of error includes determining an errorprofile, evaluating the error profile to determine a level ofreliability, determining the first error type when the level ofreliability compares favorably to a first reliability threshold anddetermining a second error type when the level of reliability comparesunfavorably to the first reliability threshold.

The processing module rebuilds the encoded data slice in accordance withthe error coding dispersal storage function to produce a rebuilt encodeddata slice when the type of error is a first error type. Next, theprocessing module stores the rebuilt encoded data slice at a differentstorage location in the corresponding addressable storage sector of theencoded data slice. The processing module determines a second errorcoding dispersal storage function when the type of error is a seconderror type. The processing module re-encodes the set of encoded dataslices based on the second error coding dispersal storage function toproduce a re-encoded set of encoded data slices. Next, the processingmodule re-defines addressable storage sectors of the single hard drivein accordance with the second error coding dispersal storage functionand an error profile of the single hard drive to produce a re-definedset of addressable storage sectors. The processing module stores there-encoded set of encoded data slices in corresponding addressablestorage sectors of the re-defined set of addressable storage sectors.

FIG. 8 is a flowchart illustrating an example of storing slices. Themethod begins with step 126 where a processing module receives data tostore and metadata. The processing module may receive the data andassociated metadata from any one of a user device, a DS processing unit,a DS managing unit, a DS unit, and a storage integrity processing unit.The data may include one or more of an encoded data slice, a datasegment, a data object, a data file, and a data stream. The metadata mayinclude one or more of a data object name, a data object size indicator,a slice name, a source name a simple object file name, a block filename, a command, a request a priority indicator, a security indicator, auser identification, a data type, a memory error indicator, a memoryavailability indicator, and a memory status.

The method continues at step 128 where the processing module determineserror coding dispersal storage function parameters. The error codingdispersal storage function parameters may include one or more of aslicing pillar width n, a read threshold k, and encoding algorithm, aslicing method, a pre-data manipulation, and a post-data manipulation.Such a determination may be based on one or more of the metadata, atable lookup, a command, the data object size indicator, a memorystatus, a memory availability indicator, a priority indicator, asecurity indicator, a user ID, and the data type. For example, theprocessing module determines the pillar width n=4 and the readthreshold=3 when the table lookup indicates a preference for a 4/3system and the memory status indicates that the memory is fullyoperational with no recent storage errors. In another example, theprocessing module determines the pillar width n=16 and the readthreshold=10 when the table lookup indicates a preference for a 16/10system when there is a history of memory errors and the memory statusindicates that the memory has recent errors.

The method continues at step 130 where the processing module determinesthe memory (e.g., memory ID) to utilize to store data slices which mayinclude one or more of one local memory device, two or more local memorydevices (e.g., in the same DS unit), and non-local memory (e.g., inanother DS unit). Such a determination may be based on one or more ofthe metadata, a table lookup, a command, a data object size indicator, amemory status, a memory availability indicator, a priority indicator, asecurity indicator, a user ID, and a data type. For example, theprocessing module determines to utilize one memory A-1 when the tablelookup indicates a preference for one memory and the memory statusindicates that the memory A-1 is fully operational with no recenterrors. In another example, the processing module determines to utilizetwo memories A-1 and B-1 when the table lookup indicates a preference toutilize at least two memory types when there is a history of memoryerrors and the memory status indicates that the memory A-1 has recenterrors.

The method continues at step 132 where the processing module definesaddressable storage sectors (e.g., of a single hard drive) to utilize inthe determined memory. The processing module defines addressable storagesectors within the single hard drive based on a number of data sliceswithin the set of data slices to produce a set of addressable storagesectors. For example, the processing module defines the addressablestorage sectors by one or more of determining utilization of the singlehard drive, avoiding an inoperable storage location of the single harddrive, avoiding a storage location of the single hard drive with ahistory of errors, and avoiding a second storage location of the singlehard drive predicted to have a future error.

The method continues with step 132 where the processing module encodesat least a portion of the data in accordance with the error codingdispersal storage function parameters to produce a set of data slices.At step 136, the processing module stores data slices of the set of dataslices in corresponding addressable storage sectors of the set ofaddressable storage sectors. At step 138, the processing module maystore one or more slice names of the data slices of the set of dataslices, identity of the set of addressable storage sectors, andutilization information associated with the data slices of the set ofdata slices in a local memory.

Alternatively, or in addition to step 134, the processing module mayencode the data in accordance with the error coding dispersal storagefunction parameters to produce a plurality of sets of data slices.Alternatively, or in addition to step 136, the processing module storesa first data slice of each of the plurality of sets of data slices in afirst addressable storage sector of the set of addressable storagesectors and the processing module stores a second data slice of each ofthe plurality of sets of data slices in a second addressable storagesector of the set of addressable storage sectors. The method to retrievethe slices and recreate the data is discussed in greater detail withreference to FIG. 9.

FIG. 9 is a flowchart illustrating an example of retrieving slices by aprocessing module where the slices may be stored in one memory. Themethod begins with step 140 where the processing module (e.g. of a DSprocessing) receives a data retrieval request from a requester. Therequester includes one of the user device, the DS processing unit, theDS managing unit, the DS unit, and the storage integrity processingunit. The processing module receives one or more of the data objectname, a data object size indicator, a slice name, a command, a priorityindicator, a security indicator, a user ID, and/or a data type with thedata object.

The method continues at step 142 where the processing module determineslocal operational parameters (e.g., error coding dispersal storagefunction parameters) which may include one or more of the pillar widthn, the read threshold, the encoding algorithm, the slicing method,pre-data manipulation, and post-data manipulation. The determination maybe based on one or more of a table lookup, a command, the data objectsize indicator, a memory status, a memory availability indicator, thepriority indicator, the security indicator, the user ID, and the datatype. For example, the processing module may determine the pillar widthn=4 and the read threshold=3 when the table lookup indicates the 4/3approach was previously utilized when the data object was stored.

The method continues with step 144 where the processing moduledetermines the memory (e.g., memory ID) to retrieve the data sliceswhich may include one or more of one memory in a DS unit, two or morememories in the DS unit, and memory in another DS unit. Such adetermination may be based on one or more of the virtual DSN address tophysical location table, a table lookup, a command, a data object sizeindicator, a memory status, a memory availability indicator, a priorityindicator, a security indicator, the user ID, and a data type. Forexample, the processing module determines to retrieve from one memoryA-1 when the table lookup indicates a preference for one memory and thememory status indicates that the memory A-1 is fully operational with norecent errors. In another example, the processing module determines toretrieve from two memories A-1 and B-1 when the table lookup indicates apreference to utilize at least two memory types when there is a historyof memory errors and the memory status indicates that the memory A-1 hasrecent errors.

The method continues at step 146 where the processing module determinesmemory locations (e.g., addresses, addressable storage sectors of asingle hard disk drive) to retrieve slices from the determined memorywhich may include one or more of to an even distribution of pillarlocations, all the pillars in sequence starting at one location, apillar distribution to avoid known memory issues, and a pillardistribution to avoid predicted future memory issues. Such adetermination may be based on one or more of the virtual DSN address tophysical location table, where last slices were stored, a table lookup,a command, the data object size indicator, a memory status, a memoryavailability indicator, a priority indicator, a security indicator, auser ID, and a data type. For example, the processing module determinesto retrieve from the even distribution of pillars when the table lookupindicates a preference for the even distribution and the memory statusindicates that the memory A-1 is fully operational with no recenterrors. In another example, the processing module determines to retrievefrom the pillar distribution to avoid known memory issues when the tablelookup indicates a preference to utilize the pillar distribution toavoid known memory issues when there is a history of memory errors andthe memory status indicates that the memory A-1 has recent errors.

The method continues with step 148 where the processing module reads thedata slices of the data from the determined memory at the determinedaddressable locations. At step 150, the processing module decodes thedata slices in accordance with the error coding dispersal storagefunction parameters to recreate the data. At step 152, the processingmodule sends the data to the requester.

FIG. 10A is a flowchart illustrating an example of rebuilding memory bya DS processing where a new memory may be populated with the informationthat was previously stored on at least one memory device. In an example,a DS unit memory fails and EC data slices are temporarily lost. The DSprocessing detects a new DS unit memory and stores recreated slices ofthe lost slices to the new memory.

The method begins with step 154 where the DS processing detects a newmemory. Note that a new memory may be a memory that was recentlyinstalled to replace a failed memory and/or a memory that was notrecently installed but idle until this point. The new memory may beavailable for utilization by the computing system to store EC dataslices. The DS processing detects a new memory by one or more of amessage, a command, a DS managing unit message, a configuration lookup,a list, a timed event, a predetermination, and a query.

At step 156, the DS processing determines if the new memory is areplacement memory (e.g., for a failed memory) based on one or more of amessage, a command, a DS managing unit message, a configuration lookup,a list, a timed event, a predetermination, and/or a query. For example,the DS processing determines the memory is not a replacement memory whenthe DS processing queries the DS units and/or memories and determinesthat they are all accounted for (e.g., actual is the same as aconfiguration lookup) with no failed memories. In another example, theDS processing determines the memory is a replacement memory when the DSprocessing queries the DS units and/or memories and determines that atleast one memory is not active (e.g., actual is not the same as aconfiguration lookup). The method branches to step 160 when the DSprocessing determines that the new memory is a replacement memory. Themethod continues to step 158 when the DS processing determines that thenew memory is not a replacement memory. At step 158, the DS processingactivates the memory in accordance with a memory expansion method toformat the memory and add the memory to an appropriate storage set(s)that require more capacity.

The method continues at step 160 where the DS processing formats the newmemory when the DS processing determines that the new memory is areplacement memory. In an instance, DS processing formats the memory bywriting the same information to all memory addresses (e.g., all zeroes,all ones, a pattern of ones and zeroes).

At step 162, the DS processing determines the slice name ranges ofmissing slices previously stored on the missing memory (e.g., a failed,inactivated, and/or removed memory). Such a determination may be basedon one or more of a lookup in the local virtual DSN address to physicallocation table, a message, a command, a DS managing unit message, aconfiguration lookup, a list, a predetermination, and a query.

At step 164, the DS processing determines the slice locations (e.g., onthe same and/or other DS units) for all other slices of the datasegments of the slice name ranges of missing slices. Such adetermination may be based on one or more of the slice name ranges ofmissing slices, a lookup in the local virtual DSN address to physicallocation table, a lookup in the virtual DSN address to physical locationtable, a message, a command, a DS managing unit message, a configurationlookup, a list, a predetermination, and/or a query.

The method continues at step 166 where the DS processing sends aretrieve slice command with slice names for all other slices of the datasegments of the slice name ranges of missing slices to the determinedslice locations. The DS processing receives the slices in response. Atstep 168, the DS processing recreates the data segments by de-slicingand decoding the received slices in accordance with the operationalparameters affiliated with the slice names. In an instance, the DSprocessing determines the operational parameters affiliated with theslice names by a user vault lookup.

At step 170, the DS processing recreates the missing slices by encodingand slicing data segments in accordance with the operational parameters.Note that the slices of the other pillars may remain stored as they wereprior to this method. Alternatively, the DS processing creates all newslices for every pillar by encoding and slicing data segments inaccordance with new operational parameters. Note that the slices arestored to the pillar(s) in the present memory and of the other pillarsto replace the previously stored slices (e.g., prior to this method).The DS processing determines the new operational parameters based on oneor more of a memory status indicator, a message, a command, a DSmanaging unit message, a configuration lookup, a list, a timed event, apredetermination, and a query. For example, the DS processing determinesthe new operational parameters to have more reliability than previouslywhen the memory failed.

At step 172, DS processing writes the missing slices to the new memoryand saves the stored locations in the local virtual DSN address tophysical location table. Note that the new memory may have more capacitythat the missing memory it is replacing. The DS processing may make theextra memory capacity available to one or more storage sets when themissing slices have been replaced as described above.

FIG. 10B is a flowchart illustrating another example of rebuildingmemory. In particular, a method is presented for use in conjunction withone or more functions and features described in conjunction with FIGS.1-10A and also FIG. 10B. The method includes step 153 where a processingmodule (e.g., of a storage unit of a dispersed storage network (DSN))detects a likelihood of having a missing encoded data slice based onlocal physical to DSN address mapping information. As a specificexample, the processing module detects the likelihood of having amissing encoded data slice by detecting replacement of a failed memorydevice. As another specific example, the processing module interpretsthe local physical to DSN address mapping information to determine thata sub-range of DSN addresses has a disproportionate amount of encodeddata slices having DSN addresses in the sub-range of DSN addresses toother sub-ranges of DSN addresses. For instance, the processing moduledetects the likelihood when the sub-range of DSN addresses includes noencoded data slices having DSN addresses in the sub-range of DSNaddresses. As yet another specific example, the processing moduleinterprets the local physical to DSN address mapping information todetermine that a sub-range of DSN addresses is not affiliated with aparticular memory device of the storage unit.

When the likelihood of having the missing encoded data slice exists, themethod continues at step 155 where the processing module sends a queryregarding the missing encoded data slice to another storage unit of theDSN. As a specific example, the processing module sends the query to theother storage unit, where the query includes a request for the relatedencoded data slice. As another specific example, the processing modulesends the query to storage units of the DSN, where the query includes arequest for other related encoded data slices of the set of encoded dataslices.

The method continues at step 157 where the processing module receives aresponse to the query from the other storage unit. As a specificexample, when the processing module sent the query to include therequest for the related encoded data slice, the processing modulereceives, as the response, the related encoded data slice from the otherstorage unit. As another specific example, when the processing modulesends the query to include the request for other related encoded dataslices, the processing module receives, as a set of responses, the otherrelated encoded data slices.

When the response includes identity of a related encoded data slice of aset of encoded data slices, the method continues at step 159 where theprocessing module commences execution of a rebuilding function togenerate a new encoded data slice to replace the missing encoded dataslice. A data segment of a data object is encoded into the set ofencoded data slices, where a threshold number of encoded data slices ofthe set of encoded data slices is required to recover the data segment.The threshold number is less than a number of encoded data slices in theset of encoded data slices. The other storage unit stores the relatedencoded data slice, where the storage unit has been assigned to store asecond encoded data slice of the set of encoded data slices, and wherethe second encoded data slice corresponds to the missing encoded dataslice.

As a specific example of commencing execution of the rebuildingfunction, when the processing module sends the query to include therequest for other related encoded data slices, and when the relatedencoded data slice and the other related encoded data slices amounts tothe threshold number, the processing module decodes the related encodeddata slice and the other related encoded data slices to recapture thedata segment and encodes the data segment to create the new encoded dataslice.

As another specific example of the commencing the execution of therebuilding function, the processing module sends requests to storageunits of the DSN regarding other related encoded data slices of the setof encoded data slices and receives, as a set of responses, the otherrelated encoded data slices. When the related encoded data slice and theother related encoded data slices amounts to the threshold number, theprocessing module decodes the related encoded data slice and the otherrelated encoded data slices to recapture the data segment and encodesthe data segment to create the new encoded data slice.

The method described above in conjunction with a storage unit canalternatively be performed by other modules of a dispersed storagenetwork or by other devices. In addition, at least one memory sectionthat stores operational instructions that can, when executed by one ormore processing modules of one or more computing devices of a dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

FIG. 11A is a schematic block diagram of another embodiment of adispersed storage unit 174 that includes a DS processing 34 and aplurality of memories 1-12. The DS processing 34 may be implemented withthe computing core 26. The memories 1-12 may be one or more of amagnetic hard disk, NAND flash, read only memory, optical disk, and anyother type of read-only or read/write memory. The memories 1-12 may beimplemented as part of or outside of the DS unit 174. For example,memories 1-4 may be implemented in the DS unit 174 and memories 5-12 maybe implemented in a remote server (e.g., a different DS unit operablycoupled to the DS unit 174 via the network). In another example,memories 1-8 are implemented with the magnetic hard disk technology andmemories 9-12 are implemented with the NAND flash technology.

The DS processing 34 may be operably coupled to the computing system viathe network 24. The DS processing 34 may receive a store command,metadata, and a data object to store. The data object may include asimple object file, a block file, and/or EC data slices. In an example,the DS processing stores the data object in one or more of the memories1-12 substantially as received (e.g., a slice is stored as a slice, ablock file is stored as a block file, etc.). In another example, the DSprocessing 34 creates EC data slices of the data object and stores theslices in one or more of the memories 1-12 as slices. Note that the DSprocessing unit determines to utilize only the memories 1-12 of the DSunit 174 when the capabilities of memories 1-12 substantially meet therequirements. In another example, a DS processing unit may determine toutilize a combination of the memories 1-12 of the DS unit 174 and memoryof at least one other DS unit when the capabilities of memories 1-12alone substantially do not meet the requirements. The method todetermine the memories to utilize is discussed in greater detail withreference to FIGS. 11B-12.

In an example, the DS processing 34 determines where (e.g., whichaddress of one or more of the memories) to store the received dataobject as EC data slices. The determination may be based on one or moreof the metadata, a command (e.g., from the DS processing unit indicatingwhich memory type to use), a type of data indicator, a local virtual DSNaddress to physical location table lookup, a priority indicator, asecurity indicator, available memory, memory performance data, memorystatus, memory cost data, and any other parameter to facilitate desiredlevels of efficiency and performance. For example, the DS processing 34may choose memories 1-12 (e.g., magnetic hard disk drives) to store theEC data slices since the performance and efficiency is good enough forthe requirements (e.g., availability, cost, response time). In anotherexample, the DS processing 34 distributes the data slices to memories1-10 when memories 11 and 12 are not available. In another example, theDS processing 34 distributes the slices at various addresses across onememory. In another example, the DS processing 34 distributes a readthreshold k=8 of the slices across memories 1-8 (for fast retrieval) andthe other 4 (n−k) slices other DS units. In yet another example, the DSprocessing 34 distributes the slices across the DS unit memories and atleast one other DS unit at the same site as the DS unit 174. In yetanother example, the DS processing 34 distributes the slices across theDS unit 174 memories and at least one other DS unit at a different siteas the DS unit 174.

The DS processing 34 utilizes a temporary set of operational parametersand a temporary set of memory choices when the memory capabilities donot meet the needs of the requirements (e.g., when a memory has failed).The method to determine the memories to utilize is discussed in greaterdetail with reference to FIGS. 11B-12. The DS processing 34 creates andmaintains the local virtual DSN address to physical memory table. The DSprocessing module 34 determines where previously stored EC data slicesare located based on the local virtual DSN address to physical memorytable upon receiving a retrieve command via the network. Note that theDS unit access may be via a WebDAV sequence, e.g., via an IP addresssuch as http://21.8.43/vault1 to facilitate easy DS unit access.

FIGS. 11B-D are schematic block diagrams of an embodiment of a dispersedstorage network (DSN) illustrating another example of operation of thedispersed storage unit 174 of FIG. 11A. The DSN includes the dispersedstorage (DS) processing unit 16 of FIG. 1, the network 24 FIG. 1, and aset of DS units 1-n. Each DS unit may be implemented utilizing the DSunit 174 of FIG. 11A. The DSN functions to store data in the set of DSunits 1-n.

FIG. 11B illustrates steps of a method to store the data. In an exampleof operation, the DS processing unit 16 dispersed storage error encodesa data segment of the data into a set of encoded data slices and sends,via the network 24, the set of encoded data slices to the DS units 1-n.Hereafter, each DS unit may be interchangeably referred to as a storageunit. Storage units of the DSN (e.g., DS units 1-n), receive the set ofencoded data slices for storage. For example, DS unit 1 (e.g., a firststorage unit) receives a first encoded data slice, DS unit 2 (e.g., asecond storage unit) receives a second encoded data slice, etc.

Having received the first encoded data slice, the DS processing 34 ofthe first storage unit determines whether to store the first encodeddata slice of the set of encoded data slices as the first encoded dataslice or as a first set of encoded data sub-slices. The determinationmay be based on one or more of metadata, a command (e.g., from the DSprocessing unit 16 indicating which memory type to use), a type of dataindicator, a local virtual DSN address to physical location tablelookup, a priority indicator, a security indicator, available memory,memory performance data, memory status, memory cost data, and any otherparameter to facilitate desired levels of efficiency and performance.

When the first encoded data slice is to be stored as the first set ofencoded data sub-slices, the DS processing 34 of the first storage unitencodes the first encoded data slice in accordance with a firstdispersed storage error encoding function to produce the first set ofencoded data sub-slices. As a specific example, the DS processing 34 ofthe first storage unit determines a desired redundancy level and whenthe desired redundancy level is based on assurances against memorydevice failure with the first storage unit, the DS processing 34 of thefirst storage unit determines the first dispersed storage error encodingfunction based on the desired redundancy level, where the firstdispersed storage error encoding function includes a pillar width numberof n, a decode threshold number of k, and where n−k is less than n/2.For instance, the DS processing 34 of the first storage unit determinesthe first dispersed storage error encoding function to include a pillarwidth of 4 and a decode threshold number of 3 and encodes the firstencoded data slice to produce encoded data sub-slices 1-1 through 1-4.

Having produced the first set of encoded data sub-slices, the DSprocessing 34 of the first storage unit identifies a first set of memorydevices within the first storage unit. For example, the DS processing 34of the first storage unit identifies memories 1-4 of the first storageunit as the first set of memory devices when memories 1-4 are available.Having identified the first set of memory devices, the DS processing 34of the first storage unit stores the first set of encoded datasub-slices in the first set of memory devices. For example, the DSprocessing 34 of the first storage unit stores the encoded datasub-slices 1-1 through 1-4 in the memory devices 1-4 of the firststorage unit.

The DS processing 34 of the second storage unit determines whether tostore the second encoded data slice of the set of encoded data slices asthe second encoded data slice or as a second set of encoded datasub-slices. When the second encoded data slice is to be stored as thesecond set of encoded data sub-slices, the second storage unit encodesthe second encoded data slice in accordance with a second dispersedstorage error encoding function to produce the second set of encodeddata sub-slices. Having produced the second set of encoded datasub-slices, the second storage unit identifies a second set of memorydevices within the second storage unit. For example, the second storageunit identifies memories 1-4 of the second storage unit. Havingidentified the second set of memory devices, the second storage unitstores the second set of encoded data sub-slices in the second set ofmemory devices.

FIG. 11C illustrates further steps of the method to store the data. Inan example of operation, the DS processing 34 of the first storage unitdetermines to store an encoded data sub-slice of the first set ofencoded data sub-slices in a memory device of another storage unit ofthe storage units, where the other storage unit is the second storageunit or a different one of the storage units. The determining may bebased on one or more determination criteria from a list of determinationcriteria. The list of determination criteria includes determining thatthe first storage unit has less than a desired amount of availablememory, determining that the first storage unit has more than a desirednumber of memory device with an age issue, and determining that theother storage unit has more available storage than the first storageunit.

Having determined to store the encoded data sub-slice in the otherstorage unit, the DS processing 34 of the first storage unit selects theother storage unit based on one or more selection criteria from a listof selection criteria. The list of selection criteria includes a queryand response with the other storage unit, a pre-establishedrelationship, an ad hoc established relationship, and a determinationthat the other storage unit has a sufficient amount of available memory.For example, the DS processing 34 of the first storage unit selects thesecond storage unit when the second storage unit has the sufficientamount of available memory.

Having selected the other storage unit, the DS processing 34 of thefirst storage unit sends, via the network 24, the encoded data sub-sliceto the other storage unit. For example, the first storage unit sendsencoded data sub-slice 1-4 of encoded data sub-slices 1-1 through 1-4 tothe second storage unit for storage. For instance, the DS processing 34of the second storage unit stores the encoded data sub-slice 1-4 inmemory 7 when memory 7 has the sufficient amount of available memory.

Having sent the encoded data sub-slice to the other storage unit, the DSprocessing 34 of the first storage unit stores remaining encoded datasub-slices of the first set of encoded data sub-slices in a set ofmemory devices within the first storage unit. For example, the DSprocessing 34 the first storage unit stores encoded data sub-slices 1-1through 1-3 in memories 1-3 of the first storage unit.

FIG. 11D illustrates further steps of the method to store the data. Inan example of operation, the DS processing 34 of the first storage unitdetermines the desired redundancy level. When the desired redundancylevel is based on assurances against failure of the first storage unit,the DS processing 34 of the first storage unit determines the firstdispersed storage error encoding function based on the desiredredundancy level, where the first dispersed storage error encodingfunction includes a pillar width number of n, a decode threshold numberof k, and where n−k is equal to or greater than n/2. For example, the DSprocessing 34 of the first storage unit determines the first dispersedstorage error encoding function to include a pillar width number of 6and a decode threshold number of 3.

Having determined the first dispersed storage error encoding function,the DS processing 34 of the first storage unit encodes the first encodeddata slice to produce the set of encoded data sub-slices. For example,the DS processing 34 of the first storage unit encodes the first encodeddata slice to produce encoded data sub-slices 1-1 through 1-6 when thepillar width number is 6. Having produced the set of encoded datasub-slices, the DS processing 34 of the first storage unit sends atleast n/2 encoded data sub-slices of the first set of encoded datasub-slices to another storage unit, where the other storage unit is thesecond storage unit or a different one of the storage units. Forexample, the DS processing 34 of the first storage unit sends encodeddata sub-slices 1-4, 1-5, and 1-6 to a second storage unit for storage.The DS processing 34 of the second storage unit stores the encoded datasub-slices 1-4, 1-5, and 1-6 in memories 9, 10, and 11 when memories 9,10, and 11 are half the sufficient amount of available memory. Havingsent the at least n/2 encoded data sub-slices of the first set ofencoded data sub-slices to the other storage unit, the DS processing 34of the first storage unit stores remaining encoded data sub-slices inmemories of the first storage unit. For example, the DS processing 34 ofthe first storage unit stores encoded data sub-slices 1-1, 1-2, and 1-3in memories 1-3 of the first storage unit.

The DS processing unit 16, upon a recovery operation to recover the datasegment, receives the first encoded data slice from at least one of thefirst storage unit and the second storage unit in response to a readslice request. For example, the DS processing 34 of the second storageunit retrieves the encoded data sub-slices 1-4, 1-5, and 1-6 from thememories 9-11 of the second storage unit, decodes the retrieved encodeddata sub-slices to reproduce the first encoded data slice, and sends,via the network 24, the reproduced first encoded data slice to the DSprocessing unit 16.

FIG. 11E is a flowchart illustrating another example of storing slices.In particular, a method is presented for use in conjunction with one ormore functions and features described in conjunction with FIGS. 1-11Dand also FIG. 11E. The method includes step 171 where one or moreprocessing modules of one or more storage units of a dispersed storagenetwork (DSN) receives a set of encoded data slices for storage, where adata segment of data is dispersed storage error encoded into the set ofencoded data slices. The method continues at step 173 where a processingmodule of a first storage unit of the storage units determines whetherto store a first encoded data slice of the set of encoded data slices asthe first encoded data slice or as a first set of encoded datasub-slices.

When the first encoded data slice is to be stored as the first set ofencoded data sub-slices, the method continues at step 175 where theprocessing module of the first storage unit encodes the first encodeddata slice in accordance with a first dispersed storage error encodingfunction to produce the first set of encoded data sub-slices. As aspecific example, the processing module of the first storage unitdetermines a desired redundancy level and when the desired redundancylevel is based on assurances against memory device failure with thefirst storage unit, the processing module of the first storage unitdetermines the first dispersed storage error encoding function based onthe desired redundancy level, where the first dispersed storage errorencoding function includes a pillar width number of n, a decodethreshold number of k, and where n−k is less than n/2.

As another specific example, having determined the desired redundancylevel, when the desired redundancy level is based on assurances againstfailure of the first storage unit, the processing module of the firststorage unit determines the first dispersed storage error encodingfunction based on the desired redundancy level, where the firstdispersed storage error encoding function includes the pillar widthnumber of n, the decode threshold number of k, and where n−k is equal toor greater than n/2.

The method continues at step 177 where the processing module of thefirst storage unit identifies a first set of memory devices. As aspecific example, the first storage unit identifies the first set ofmemory devices within the first storage unit. The method continues atstep 179 where the processing module of the first storage unit storesthe first set of encoded data sub-slices. As a specific example, theprocessing module of the first storage unit stores the first set ofencoded data sub-slices in the first set of memory devices.

As another specific example, the processing module of the first storageunit determines to store an encoded data sub-slice of the first set ofencoded data sub-slices in a memory device of another storage unit ofthe storage units, where the other storage unit is a second storage unitor a different one of the storage units. The processing module of thefirst storage unit selects the other storage unit based on one or moreselection criteria from a list of selection criteria. The list ofselection criteria includes a query and response with the other storageunit, a pre-established relationship, an ad hoc establishedrelationship, and a determination that the other storage unit has asufficient amount of available memory. The determining to store theencoded data sub-slice in the other storage unit may be based on one ormore determination criteria from a list of determination criteria, wherethe list of determination criteria includes determining that the firststorage unit has less than a desired amount of available memory,determining that the first storage unit has more than a desired numberof memory device with an age issue, and determining that the otherstorage unit has more available storage than the first storage unit.

Having determined to store the encoded data sub-slice of the otherstorage unit, the processing module of the first storage unit sendsencoded data sub-slice to the other storage unit for storage. Theprocessing module of the first storage unit stores remaining encodeddata sub-slices of the first set of encoded data sub-slices in a set ofmemory devices within the first storage unit. As yet another specificexample, when n−k is equal to or greater than n/2, the processing moduleof the first storage unit sends at least n/2 encoded data sub-slices ofthe first set of encoded data sub-slices to the other storage unit,where the other storage unit is the second storage unit or a differentone of the storage units.

The method continues at step 181 where a processing module of a secondstorage unit of the storage units determines whether to store a secondencoded data slice of the set of encoded data slices as the secondencoded data slice or as a second set of encoded data sub-slices. Whenthe second encoded data slice is to be stored as the second set ofencoded data sub-slices, the processing module of the second storageunit encodes the second encoded data slice in accordance with a seconddispersed storage error encoding function to produce the second set ofencoded data sub-slices.

The method continues at step 185 where the processing module of thesecond storage unit identifies a second set of memory devices. Forexample, the processing module of the second storage unit identifies thesecond set of memory devices within the second storage unit. The methodcontinues at step 187 where the processing module of the second storageunit stores the second set of encoded data slices. For example, theprocessing module of the second storage unit stores the second set ofencoded data sub-slices in the second set of memory devices.

The method described above in conjunction with a processing module canalternatively be performed by other units of a dispersed storage networkor by other devices. In addition, at least one memory section thatstores operational instructions that can, when executed by one or moreprocessing modules of one or more computing devices of a dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

FIG. 12 is another flowchart illustrating another example of storingslices by a DS processing 34 where the DS processing 34 determines whichmemories of a DS unit 174 or of one or more other DS units to utilize asdiscussed below. The method begins with step 176 where the DS processingreceives a data object to store from the user device, the DS processingunit, the DS managing unit, the DS unit, and/or the storage integrityprocessing unit. The DS processing may receive one or more of the dataobject name, a data object size indicator, a slice name, a simple objectfile, a block file, a command, a priority indicator, a securityindicator, a user ID, and a data type with the data object.

The method continues at step 178 where the DS processing determinesmemory status of the memory of the DS unit and/or the memory of one ormore other DS units. Such a determination may be based on one or more ofa lookup, a command, a query, and/or a DS managing unit message. Forexample, the DS processing may determine that memory 5 is unavailablevia a query. In an instance, the DS processing determines that thememory status is not fully operational if at least one memory is notavailable. In another instance, the DS processing determines that thememory status is fully operational when all of the memories areavailable. The method branches to step 196 when the DS processingdetermines that the memory status is fully operational. The methodcontinues to step 180 when the DS processing determines that the memorystatus is not fully operational.

At step 180, the DS processing determines temporary operationalparameters which may include one or more of the pillar width n, the readthreshold, the encoding algorithm, the slicing method, pre-datamanipulation, and post-data manipulation. Such a determination may bebased on one or more of which memory is not available, how many memoriesare not available, a table lookup, a command, the data object sizeindicator, a memory status, a memory availability indicator, thepriority indicator, the security indicator, the user ID, and the datatype. For example, the DS processing may determine the pillar width n=6and the read threshold=4 when the memory status indicates that memories10-12 are unavailable. In this example, the DS processing subsequentlystores the 6 pillars in 6 of the remaining 9 available memories. Inanother example, the DS processing may determine the pillar width n=12and the read threshold=8 when the memory status indicates that memory 5is unavailable. In this example, the DS processing subsequently stores11 of the 12 pillar slices in 11 of the remaining 11 available memoriesand temporarily stores the 12^(th) pillar slices in one of the memoriesand/or in another DS unit. In addition, the DS processing maysubsequently move the temporarily stored slices to memory 12 when memory12 is available.

At step 182, the DS processing determines temporary memory (e.g., memoryID) or memories to utilize to store the slices which may include one ormore of one memory in the DS unit, a spare memory, an unused memory, twoor more memories in the DS unit, and/or memory in another DS unit. Sucha determination may be based on one or more of which memory is notavailable, how many memories are not available, a table lookup, acommand, the data object size indicator, a memory status, a memoryavailability indicator, the priority indicator, the security indicator,the user ID, and the data type. For example, the DS processingdetermines to utilize temporary memories 1-4 and 6-12 to store 11 of the12 pillar slices (e.g., with 12/8 operational parameters) and memory 1to store the 12^(th) pillar slices when memory 5 is unavailable.

At step 184, the DS processing determines temporary memories locations(e.g., addresses) to utilize in the determined temporary memory to storethe slices which may include one or more of an even distribution ofpillar locations, all the pillars in sequence starting at one location,a pillar distribution to avoid known memory issues, and a pillardistribution to avoid predicted future memory issues. The locationdetermination may be based on one or more of where last slices werestored, a table lookup, a command, the data object size indicator, amemory status, a memory availability indicator, the priority indicator,the security indicator, the user ID, and the data type.

The method continues at step 186 where the DS processing creates the ECdata slices of the data object in accordance with the temporaryoperational parameters. At step 188, the DS processing writes the slicesto the determined temporary memories at the determined temporarymemories locations. At step 190, the DS processing saves the slice name,temporary memory ID, temporary memory locations (e.g., startingaddress), and sizes of the slices in the virtual DSN address to physicallocation table to facilitate subsequent retrieval of the data object.

The method continues at step 192 where the DS processing determinesmemory status of the DS unit and/or the memory of one or more other DSunits to determine if memory that was unavailable is now available. Sucha determination may be based on one or more of a lookup, a command, aquery, and/or a DS managing unit message. For example, the DS processingdetermines that memory 5 is now available via a query. The DS processingdetermines that the memory status is not fully operational if at leastone memory is not available. The DS processing determines that thememory status is fully operational when all of the memories areavailable. The method branches back step 192 when the DS processingdetermines that the memory status is not fully operational. The methodcontinues step 194 when the DS processing determines that the memorystatus is fully operational.

The method continues at step 194 where the DS processing retrieves theslices from the temporary memories at the temporary memories locations.Next, the DS processing recreates the data object in accordance with thetemporary operational parameters. The method continues to step 196.

At step 196, the DS processing determines local operational parameters,which may include one or more of the pillar width n, the read threshold,the encoding algorithm, the slicing method, pre-data manipulation, andpost-data manipulation. Such a determination may be based on one or moreof a table lookup, a command, the data object size indicator, a memorystatus, a memory availability indicator, the priority indicator, thesecurity indicator, the user ID, and the data type. For example, the DSprocessing may determine the pillar width n=12 and the read threshold=8when the table lookup indicates a preference for a 12/8 system (e.g., toutilize the memory configuration of memories 1-12) and the memory statusindicates that the memory is fully operational with no recent errors.

At step 198, the DS processing determines the memories (e.g., memory ID)to utilize to store the slices, which may include one or more of onememory in the DS unit, two or more memories in the DS unit, and memoryin another DS unit. Such a determination may be based on one or more ofa table lookup, a command, the data object size indicator, a memorystatus, a memory availability indicator, the priority indicator, thesecurity indicator, the user ID, and the data type.

At step 200, the DS processing determines memories locations (e.g.,addresses) to utilize in the determined memories to store the sliceswhich may include one or more of, but not limited to an evendistribution of pillar locations, all the pillars in sequence startingat one location, a pillar distribution to avoid known memory issues, anda pillar distribution to avoid predicted future memory issues. Thelocation determination may be based on one or more of where last sliceswere stored, a table lookup, a command, the data object size indicator,a memory status, a memory availability indicator, the priorityindicator, the security indicator, the user ID, and the data type.

At step 202, the DS processing creates the EC data slices of the dataobject in accordance with the local operational parameters. At step 204,the DS processing writes the slices to the determined memories at thedetermined memories locations. At step 206, the DS processing saves theslice name, memory ID, memories locations (e.g., starting address), andsizes of the slices in the virtual DSN address to physical locationtable to facilitate subsequent retrieval of the data object.

FIG. 13 is a schematic block diagram of another embodiment of acomputing system that includes a plurality of DS units 1-7 where atleast one of the plurality of DS units 1-7 includes a DS processing 34to create slices to be stored in one or more of the plurality of DSunits 1-7. The DS units 1-7 may be installed at one or more sites. Forexample, DS unit 1 208 may be at site 1, DS units 2-4 may be at site 2,and DS units 5-7 may be at site 3.

As illustrated, the DS unit 1 208 at site 1 may include the DSprocessing 34 and a plurality of memories 1-12. The DS processing 34 maybe implemented with the computing core 26. The memories 1-12 may be oneor more of a magnetic hard disk, NAND flash, read only memory, opticaldisk, and any other type of read-only or read/write memory. The memories1-12 may be implemented as part of or outside of the DS unit 208. Forexample, memories 1-4 may be implemented in the DS unit 208 and memories5-12 may be implemented in a remote server (e.g., a different DS unitoperably coupled to the DS unit 208 via the network 24). In anotherexample, memories 1-8 are implemented with the magnetic hard disktechnology and memories 9-12 are implemented with the NAND flashtechnology.

As illustrated, the DS units 2-7 each include memories 1-4. In thisinstance, DS units 2-7 do not include the DS processing 34. The DSprocessing 34 of DS unit 208 is operably coupled to DS units 2-7 tofacilitate storing and retrieving of data to and from the DS unit 2-7memories 1-4. The DS processing 34 may be operably coupled to thecomputing system via the network to four. The DS processing 34 mayreceive a store command, metadata, and a data object to store. The dataobject may include a simple object file, a block file, and/or EC dataslices. In an example, the DS processing 34 stores the data object inone or more of the memories 1-12 substantially as received (e.g., aslice is stored as a slice, a block file is stored as a block file,etc.). In another example, the DS processing 34 creates EC data slicesof the data object and stores the slices in one or more of the memories1-12 as slices. Note that a DS processing unit may determine to utilizeonly memories 1-12 of the DS unit 208 when the capabilities of memories1-12 substantially meet the requirements. In another example, the DSprocessing unit may determine to utilize some combination of thememories 1-12 of the DS unit 208 and memory of at least one other DSunit 2-7 when the capabilities of memories 1-12 alone do notsubstantially meet the requirements.

In an example, the DS processing 34 of DS unit 208 determines where(e.g., which address of one or more of the memories) to store thereceived data object as EC data slices. Such a determination may bebased on one or more of the metadata, a command (e.g., from the DSprocessing unit indicating which memory type to use), a type of dataindicator, a local virtual DSN address to physical location tablelookup, a priority indicator, a security indicator, available memory,memory performance data, memory status, memory cost data, and any otherparameter to facilitate desired levels of efficiency and performance.For example, the DS processing 34 may choose memories 1-12 (e.g.,magnetic hard disk drives) to store the EC data slices since theperformance and efficiency is good enough for the requirements (e.g.,availability, cost, response time). In another example, the DSprocessing 34 distributes the slices to memories 1-10 when memories 11and 12 are not available. In another example, the DS processing 34distributes the slices at various addresses across one memory. Inanother example, the DS processing 34 distributes a read threshold k=8of the slices across memories 1-8 (to enable fast retrieval) and theother 4 (n−k) slices to DS units 2-7. In yet another example, the DSprocessing 34 distributes the slices across the DS unit memories and atleast one other DS unit 2-7.

The DS processing 34 creates and maintains the local virtual DSN addressto physical memory table. The DS processing module 34 determines wherepreviously stored EC data slices are located based on the local virtualDSN address to physical memory table upon receiving a retrieve commandvia the network. Note that the DS unit 208 access may be via a WebDAVsequence, e.g., via an IP address such as http://21.8.43/vault1 tofacilitate easy DS unit 208 access.

The plurality of DS units may include one, two, three, or more DS unitsat any point in time. For example, the system may start with DS unit 208at site 1 and may add DS unit 2 at site 2 at a subsequent time. The DSprocessing 34 may detect that DS unit 2 was added and may move a portionof stored data from the memories of DS unit 208 to DS unit 2 inresponse. In another example, DS unit 5 may be added at a still furthersubsequent time. The DS processing before may detect that DS unit 5 wasadded and may move a portion of stored data from DS unit 208 and DS unit2 to DS unit 5 in response.

In another example, the DS processing 34 may move all 12 pillars ofslices from the memories 1-12 of DS unit 208 to memories 1-4 of DS units2-4 when the DS processing 34 detects that the site 2 DS units 2-4 areavailable. Still later, the DS processing 34 may redistribute all 12pillars of slices from the memories 1-4 of DS units 2-4 to memories 1-4of DS units 2-7 when the DS processing detects that the site 3 DS units5-7 are also available. The method to determine added DS units and tomove a portion of the data will be discussed in greater detail withreference to FIG. 14.

FIG. 14 is a flowchart illustrating an example of distributing slices.The method begins at step 210 where a DS processing determines if the DSunit storage set configuration has changed. A configuration change mayinclude the addition or subtraction of DS units assigned as pillars ofcommon storage sets. The DS units may comprise pillars at one or moresites. Such a determination may be based on one or more of a command, anew configuration message from the DS managing unit, a lookup, and aquery. The method repeats step 210 when the DS processing determinesthat the DS unit storage set configuration has not changed. The methodbranches to step 212 when the DS processing determines that the DS unitstorage set configuration has changed.

At step 212, the DS processing determines the new storage set and newoperational parameters. The new storage set determination may be basedon one or more of the current storage set configuration, the location ofa new DS unit, DS unit capabilities, predetermined storage setconfiguration goals, a command, a new configuration message from the DSmanaging unit, a lookup, and a query. For example, the DS processingdetermines the new storage set to replace a current storage set wherethe new storage set will utilize more sites to improve reliability whenthe predetermined storage set configuration goals indicate morereliability and the storage set change enables at least one new site.

At step 212, the determination of the operational parameters may bebased on one or more of the new storage set, the current operationalparameters, the current storage set configuration, the location of a newDS unit, DS unit capabilities, predetermined storage set configurationgoals, a command, a new configuration message from the DS managing unit,a lookup, and a query. For example, the DS processing determines the newoperational parameters to replace the current operational parameterswhere the new operational parameters will utilize more pillars toimprove reliability when the predetermined storage set configurationgoals indicate more reliability and the storage set change enables atleast one new pillar.

The method continues at step 214 where the DS processing determines whatportion of the slices to move based on one or more of, but not limitedto the new storage set, the new operational parameters, the currentoperational parameters, the current storage set configuration, a currentmemory utilization indicator, an amount of data stored indicator, acurrent storage set performance indicator, a new storage set capacityindicator, the location of a new DS unit, DS unit capabilities,predetermined storage set configuration goals, a command, a newconfiguration message from the DS managing unit, a lookup, and a query.For example, the DS processing determines the portion of the slices tomove to be 25% when the current memory utilization indicator has notreached a high threshold and the new storage set capacity indicator isat least a threshold greater than the amount of data to be moved.

At step 216, the DS processing retrieves slices from the current storageset in accordance with the current operational parameters based on alookup in a local DSN address to physical location table. The sliceretrieval may include reading slices from the DS unit memories and/orsending a retrieve slice command to one or more DS units. The DSprocessing reads the slices from memory and/or receives the slices inmessage(s) from other DS unit(s).

At step 218, the DS processing recreates data segments and data objectsby de-slicing and decoding the read and/or received slices in accordancewith the current operational parameters. At step 220, the DS processingcreates slices of the data objects in accordance with the newoperational parameters. At step 222, the DS processing writes slices tothe DS unit memory (for pillars of the DS unit) and/or sends slices witha store command for storage of slices in other DS unit(s) where the DSunit and the other DS unit(s) comprise the new storage set. The DSprocessing saves the storage locations of the slices in the localvirtual DSN address to physical location table to be utilized insubsequent data object retrieval.

FIG. 15A is a schematic block diagram of another embodiment of acomputing system. As illustrated, the system includes a DS managing unit18 and a plurality of DS units 1-4. The DS units 1-4 may be allocated toone or more DS unit storage sets 1-2 (e.g., a set of DS units where thepillars resulting from encoding and slicing of data segments of a uservault are stored). For example, DS units 1-3 comprise storage set 1 andDS units 2-4 comprise storage set 2.

In an example of operation, the DS managing unit 18 determines an amountof memory allocated to the storage set where the allocation is theamount of available memory the storage set may utilize. Such adetermination may be based on one or more of a user vault lookup, apredetermination, the number of system users, the estimated memory useper user, the actual memory use per user, the memory capacity of DSunits, the current amount of memory utilization, the amount of unusedcapacity, a command, an adaptive algorithm, memory status, an errormessage, and an external input. For example, the DS managing unit 18determines the amount of memory allocated to the storage set to be 100terabytes when the amount of unused capacity is above a first thresholdand the estimated memory use per user is below a second threshold.

In another example, the DS managing unit 18 determines the amount ofmemory allocated to the vault(s) that utilize the storage set where theallocation is the amount of available memory the vault may utilize. Sucha determination may be based on one or more of a subscription indicator,a user vault lookup, a predetermination, the number of system users, theestimated memory use per user, the actual memory use per user, thememory capacity of DS units, the current amount of memory utilization,the amount of unused capacity, a command, an adaptive algorithm, memorystatus, an error message, and an external input. For example, the DSmanaging unit determines the amount of memory allocated to vault 1 to be30 terabytes when the amount of unused capacity is above a firstthreshold and the estimated memory use per user is below a secondthreshold.

The DS managing unit 18 sends a memory allocation information message tothe DS units 1-4 of the storage set that contains memory allocationinformation. The memory allocation information may include one or moreof, but not limited to the amount of memory allocated to the storageset, vault IDs that may utilize the storage set, other DS unit IDs ofthe storage set, and/or storage set operational parameters (e.g., pillarwidth n). The DS unit saves the memory allocation information includingthe amount of memory allocated to all of the storage set(s) that includethe DS unit. For example, DS unit 1 saves the 100 terabyte allocation tostorage set 1, DS units 2 and 3 saves the 100 terabyte allocation tostorage set 1 and a 100 terabyte allocation to storage set 2, and DSunit 4 saves the 100 terabyte allocation to storage set 2.

In an instance, DS unit 1 determines when to analyze the memoryutilization to produce utilization information 224 that the DS unit 1sends to the DS managing unit. The utilization information 224-230 mayinclude one or more of vault utilization of memory (e.g., how much isactually stored) per storage set, total memory utilization of all vaultsper storage set, total memory used, and/or free memory space. The DSunits 1-4 determine when to analyze the memory utilization based on oneor more of a time duration since the last analysis, a storage sequence,a time schedule, a command, a message from the DS managing unit, and areceived query. For example, DS unit 2 determines to analyze the memoryutilization immediately when receiving a store slice command. In anotherexample, the DS unit 3 determines to analyze the memory utilization onceevery day at 3 AM when the time schedule indicates a daily analysis at 3AM.

The DS units 1-4 determine the memory utilization and producesutilization information 224-230. For example, the DS unit 1 determinesthat vault 1 is utilizing 26 terabytes of storage set 1, vault 2 isutilizing 20 terabytes of storage set 1, and storage set 1 has 54terabytes of free space. Note that the memory utilization may beexpressed as total vault utilization (e.g., based on DS unit specificutilization and the pillar width of the vault) and/or DS unit specificutilization. For example, the vault 1 DS unit 1 utilization may be 8.66terabytes and the vault 1 pillar width=3 such that the total vault 1utilization is 3×8.66 terabytes=26 terabytes. In another memoryutilization example, the DS unit 2 determines that vault 1 is utilizing26 terabytes of storage set 1, vault 2 is utilizing 20 terabytes ofstorage set 1, storage set 1 has 54 terabytes of free space, vault 1 isutilizing 42 terabytes of storage set 2, and storage set 2 has 58terabytes of free space. In another memory utilization example, the DSunit 4 determines that vault 1 is utilizing 42 terabytes of storage set2 and storage set 2 has 58 terabytes of free space.

The DS units 1-4 send the memory utilization information 224-230 to oneor more of the DS managing unit, the DS processing unit, the userdevice, and the storage integrity processing unit when the DS unit 1-4determines the memory utilization information 224-230. The DS managingunit 18 receives the memory utilization information 224-230 from the DSunits 1-4 and aggregates the information. The DS managing unit on itdetermines the vault utilization and unused capacity and takes action ifeither or both do not compare favorably to thresholds. The method toprocess the received memory utilization information 224-230 by the DSmanaging unit is discussed in greater detail with reference to FIG. 16.

Note that a simple file object vault may not be pre-defined such thatwriting data increases memory utilization and deleting data lowers thememory utilization. Further note that in a block vault may bepre-defined (e.g., pre-allocated) such that writing data does notincrease memory utilization and deleting data does not lower the memoryutilization.

FIG. 15B is a schematic block diagram of another embodiment of acomputing system that includes the dispersed storage (DS) managing unit18 of FIG. 15A, DS units 1-4 of FIG. 15A, and the DS processing unit 16of FIG. 1. The DS units may be organized into two or more storage sets.For example, a storage set 1 (e.g., a first set of storage units)includes DS units 1-3 and a storage set 2 (e.g., a second set of storageunits) includes DS units 2-4. Hereafter, a DS unit may beinterchangeably referred to as a storage unit. The first and second setsof storage units of a plurality of storage units support a first logicalstorage vault, where the first and second sets of storage units includesat least one common storage unit (e.g., DS units 2 and 3). For example,the first and second sets storage units support a vault 1 while thefirst set of storage units supports a vault 2.

In an example of operation, the DS managing unit 18 obtains utilizationinformation regarding the plurality of storage units of the DSN. Theutilization information of a storage unit of the plurality of storageunits includes a listing of logical storage vaults supported by thestorage unit and storage capacity consumed for each logical storagevault listed in the listing of logical storage vaults. The utilizationinformation and may further include one or more of available storagecapacity of the storage unit and storage capacity trend data. The firstlogical storage vault stores a plurality of encoded data objects. Anencoded data object of the plurality of encoded data objects consists ofa data object being dispersed storage error encoded into a plurality ofsets of encoded data slices. For example, the DS processing unit 16dispersed storage error encodes the data object to produce the pluralityof sets of encoded data slices for storage in at least one storage setassociated with the first logical storage vault.

The DS managing unit 18 obtains utilization information by one ofquerying the plurality of storage units for the utilization information,receiving the utilization information from the plurality of storageunits, or retrieving the utilization information. As a specific exampleof the obtaining of the utilization information, the DS managing unit 18receives the utilization information from the DS units 1-4 indicatingthat a total of the 120 TB of encoded data objects is stored in thestorage set 1 for the first logical storage vault, a total of another 90TB of encoded data objects is stored in the storage set 2 for the firstlogical storage vault, and a total of 60 TB of encoded data objects isstored in the storage set 1. As another specific example of theobtaining of the utilization information, the DS managing unit 18receives further utilization information indicating that the DS unit 1is storing 60 TB of the encoded data objects and DS unit 4 is storing 30TB of the encoded data objects, where the DS unit 1 is storing 40 TB ofthe encoded data objects associated with the first logical storage vaultand the DS unit 4 is storing 30 TB of encoded data objects associatedwith the first logical storage vault.

Having obtained the utilization information, the DS managing unit 18detects a utilization imbalance between a first storage unit of thefirst set of storage units and a second storage unit of the second setof storage units based on the utilization information, where the firstand second storage units are not the common storage unit. As a specificexample, the DS managing unit 18 detects a utilization imbalance betweenDS unit 1 and DS unit 4 when the utilization information indicates thatDS unit 1 is storing 60 TB of the encoded data objects and DS unit 4 isstoring 30 TB of the encoded data objects.

Having detected the utilization imbalance, at least one of the DSmanaging unit 18 and the DS processing unit 16 executes a data storagefunction regarding the first logical storage vault based on theutilization imbalance. As a specific example of executing the datastorage function, the DS processing unit 16 receives a write request asthe data storage function, selects the first set of storage units or thesecond set of storage units based on the utilization imbalance forstoring a first data object associated with the write request to producea selected set of storage units (e.g., the storage set 2), andfacilitates storage of the first data object in the selected set ofstorage units. In an instance of facilitating storage of the first dataobject, the DS processing unit 16 dispersed storage error encodes thefirst data object to produce a first plurality of sets of encoded dataslices and sends write commands to the storage units of the selected setof storage units regarding storage of the first plurality of sets ofencoded data slices.

As another specific example of executing the data storage function, theDS processing unit 16 determines that utilization of the first storageunit has reached a utilization threshold of the first storage unit,determines that utilization of the second storage unit is below autilization threshold of the second storage unit, identifies encodeddata slices of selected sets of encoded data slices of the plurality ofsets of encoded data slices to migrate stored by the first storage unit,and migrates the encoded data slices of selected sets of encoded dataslices from the first storage unit to the second storage unit. Forexample, the DS processing unit 16 identifies 15 TB of encoded dataslices stored in the DS unit 1 for migration to the DS unit 4, where the15 TB of encoded data slices associated with the first logical storagevault. In an instance, DS processing unit 16 retrieves the 15 TB ofencoded data slices from the DS unit 1 and sends the 15 TB of encodeddata slices to the DS unit 4 for storage. As such, the imbalance iscured as each of the DS unit 1 and 4 store 45 TB of encoded data objectsafter the migration.

Having executed the data storage function, at least one of the DSprocessing unit 16 and the DS managing unit 18 updates storage locationinformation of the encoded data slices of selected sets of encoded dataslices as currently being stored by the second storage unit. Forexample, the DS processing unit 16 updates the storage locationinformation to indicate that the 15 TB of encoded data slices isassociated with the DS unit 4 and is associated with the DS unit 1. Assuch, performance of retrieval of the data object may be enhanced byretrieving encoded data slices from the storage set 2.

FIG. 16A is a flowchart illustrating an example of determining memoryutilization. The method begins with step 232 where a DS managing unitreceives memory utilization information from a DS unit. At step 234, theDS managing unit aggregates the memory utilization information per vaultto produce vault utilization. For example, the DS managing unit adds thereceived memory utilization information from a DS unit 3 that vault 1 isutilizing 26 terabytes of storage set 1 to the received memoryutilization information from the DS unit 3 that vault 1 is utilizing 42terabytes of storage set 2 for a total of 68 terabytes.

The method continues with step 236 where the DS managing unit determinesstorage set unused capacity based on the received memory utilizationinformation. For example, storage set 1 has 54 terabytes of unusedcapacity and storage set 2 has 58 terabytes of unused capacity. At step238, the DS managing unit determines if vault utilization comparesfavorably to a utilization threshold. For example, the DS managing unitdetermines that the vault utilization compares favorably to theutilization threshold when the vault 1 utilization is 68 terabytes andthe utilization threshold is 150 terabytes. Note that the DS managingunit determines the utilization threshold based on one or more of, butnot limited to a predetermined value, a user vault lookup, apredetermination, a command, an input to the DS managing unit, and/or adynamic value. The method branches step 242 when the DS managing unitdetermines that the vault utilization compares favorably to theutilization threshold. The method continues to the step 240 when the DSmanaging unit determines that the vault utilization does not comparefavorably to the utilization threshold. At step 240, the DS managingunit sends an alert message (e.g., to the user device, DS unit, DSprocessing unit, and/or a manager station) containing the vault ID ofthe vault with the unfavorable vault utilization. Alternatively, or inaddition to, the DS managing unit may perform one or more of modifyingthe utilization threshold, modifying the amount of memory allocated tothe storage set of the vault, delete a portion of the slices stored inthe vault, and move a portion of the slices stored in the vault toanother storage set. Note that the DS managing unit may repeat the stepsabove for each vault.

The method continues at step 242 where the DS managing unit determinesif unused capacity compares favorably to a capacity threshold. Forexample, the DS managing unit determines that the unused capacitycompares favorably to the capacity threshold when the storage set 1 freespace is 54 terabytes and the capacity threshold is 10 terabytes. Notethat the DS managing unit determines the capacity threshold based on oneor more of a historic memory usage factor, a predetermined value, a uservault lookup, a predetermination, a command, an input to the DS managingunit, and a dynamic value. The method repeats back to step 232 when theDS managing unit determines that the unused capacity compares favorablyto the capacity threshold. The method continues to step 244 when the DSmanaging unit determines that the unused capacity does not comparefavorably to the capacity threshold. At step 244, the DS managing unitallocates more memory to the storage set. Alternatively, or in additionto, the DS managing unit performs one or more of sending an alertmessage (e.g., to the user device, DS unit, DS processing unit, and/or amanager station) containing the storage set ID with the unfavorableunused capacity, modifying the capacity threshold, deleting a portion ofthe slices stored in the storage set, and/or moving a portion of theslices stored in the storage set to another storage set. The methodbranches back to step 232.

FIG. 16B is a flowchart illustrating another example of determiningmemory utilization. In particular, a method is presented for use inconjunction with one or more functions and features described inconjunction with FIGS. 1-5, 15A-16A and also FIG. 16B. The methodincludes step 250 where a processing module of a dispersed storagenetwork (DSN) obtains utilization information regarding a plurality ofstorage units of the DSN, where first and second sets of storage unitsof the plurality of storage units support a first logical storage vault.The first and second sets of storage units includes a common storageunit. The utilization information of a storage unit of the plurality ofstorage units includes a listing of logical storage vaults supported bythe storage unit and storage capacity consumed for each logical storagevault listed in the listing of logical storage vaults. The first logicalstorage vault stores a plurality of encoded data objects, where anencoded data object of the plurality of encoded data objects consists ofa data object being dispersed storage error encoded into a plurality ofsets of encoded data slices. The processing module obtains theutilization information by one of querying the plurality of storageunits for the utilization information, receiving the utilizationinformation from the plurality of storage units, or retrieving theutilization information.

The method continues at step 252 where the processing module detects autilization imbalance between a first storage unit of the first set ofstorage units and a second storage unit of the second set of storageunits based on the utilization information, where the first and secondstorage units are not the common storage unit. The method continues atstep 254 where the processing module executes a data storage functionregarding the first logical storage vault based on the utilizationimbalance.

As a specific example of the executing the data storage function, theprocessing module receives a write request as the data storage function,selects the first set of storage units or the second set of storageunits based on the utilization imbalance for storing a first data objectassociated with the write request to produce a selected set of storageunits, and facilitates storage of the first data object in the selectedset of storage units. The facilitating storage of the first data objectincludes dispersed storage error encoding the first data object toproduce a first plurality of sets of encoded data slices and sendingwrite commands to the storage units of the selected set of storage unitsregarding storage of the first plurality of sets of encoded data slices.

As another specific example of the executing the data storage function,the processing module determines that utilization of the first storageunit has reached a utilization threshold of the first storage unit,determines that utilization of the second storage unit is below autilization threshold of the second storage unit, identifies encodeddata slices of selected sets of encoded data slices of the plurality ofsets of encoded data slices to migrate stored by the first storage unit,and migrates the encoded data slices of selected sets of encoded dataslices from the first storage unit to the second storage unit.

The method continues at step 256 where the processing module updatesstorage location information of the encoded data slices of selected setsof encoded data slices as currently being stored by the second storageunit. For example, the processing module associates slice names of theselected sets of encoded data slices with the second storage unit anddisassociates the slice names of the selected sets of encoded dataslices with the first storage unit.

The method described above in conjunction with a processing module canalternatively be performed by other units of a dispersed storage networkor by other devices. In addition, at least one memory section thatstores operational instructions that can, when executed by one or moreprocessing modules of one or more computing devices of a dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described, at least in part, in terms ofone or more embodiments. An embodiment of the present invention is usedherein to illustrate the present invention, an aspect thereof, a featurethereof, a concept thereof, and/or an example thereof. A physicalembodiment of an apparatus, an article of manufacture, a machine, and/orof a process that embodies the present invention may include one or moreof the aspects, features, concepts, examples, etc. described withreference to one or more of the embodiments discussed herein.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

What is claimed is:
 1. A method for execution by one or more processingmodules of one or more computing devices of a dispersed storage network(DSN), the method comprises: receiving, by storage units of the DSN, aset of encoded data slices for storage, wherein a data segment of datais dispersed storage error encoded into the set of encoded data slices;determining, by a first storage unit of the storage units, whether tostore a first encoded data slice of the set of encoded data slices asthe first encoded data slice or as a first set of encoded datasub-slices; when the first encoded data slice is to be stored as thefirst set of encoded data sub-slices, encoding, by the first storageunit, the first encoded data slice in accordance with a first dispersedstorage error encoding function to produce the first set of encoded datasub-slices; determining, by a second storage unit of the storage units,whether to store a second encoded data slice of the set of encoded dataslices as the second encoded data slice or as a second set of encodeddata sub-slices; and when the second encoded data slice is to be storedas the second set of encoded data sub-slices, encoding, by the secondstorage unit, the second encoded data slice in accordance with a seconddispersed storage error encoding function to produce the second set ofencoded data sub-slices.
 2. The method of claim 1 further comprises:identifying, by the first storage unit, a first set of memory deviceswithin the first storage unit; storing, by the first storage unit, thefirst set of encoded data sub-slices in the first set of memory devices;identifying, by the second storage unit, a second set of memory deviceswithin the second storage unit; and storing, by the second storage unit,the second set of encoded data sub-slices in the second set of memorydevices.
 3. The method of claim 1 further comprises: determining, by thefirst storage unit, to store an encoded data sub-slice of the first setof encoded data sub-slices in a memory device of another storage unit ofthe storage units, wherein the other storage unit is the second storageunit or a different one of the storage units; sending, by the firststorage unit, the encoded data sub-slice to the other storage unit; andstoring, by the first storage unit, remaining encoded data sub-slices ofthe first set of encoded data sub-slices in a set of memory deviceswithin the first storage unit.
 4. The method of claim 3 furthercomprises: selecting the other storage unit based on one or moreselection criteria from a list of selection criteria, wherein the listof selection criteria includes: a query and response with the otherstorage unit; a pre-established relationship; an ad hoc establishedrelationship; and a determination that the other storage unit has asufficient amount of available memory.
 5. The method of claim 3 furthercomprises: determining to the store the encoded data sub-slice in theother storage unit based on one or more determination criteria from alist of determination criteria, wherein the list of determinationcriteria includes: determining that the first storage unit has less thana desired amount of available memory; determining that the first storageunit has more than a desired number of memory device with an age issue;and determining that the other storage unit has more available storagethan the first storage unit.
 6. The method of claim 1 further comprises:determining, by the first storage unit, a desired redundancy level; andwhen the desired redundancy level is based on assurances against memorydevice failure with the first storage unit, determining, by the firststorage unit, the first dispersed storage error encoding function basedon the desired redundancy level, wherein the first dispersed storageerror encoding function includes a pillar width number of n, a decodethreshold number of k, and where n−k is less than n/2.
 7. The method ofclaim 1 further comprises: determining, by the first storage unit, adesired redundancy level; when the desired redundancy level is based onassurances against failure of the first storage unit, determining, bythe first storage unit, the first dispersed storage error encodingfunction based on the desired redundancy level, wherein the firstdispersed storage error encoding function includes a pillar width numberof n, a decode threshold number of k, and where n−k is equal to orgreater than n/2; and sending, by the first storage unit, at least n/2encoded data sub-slices of the first set of encoded data sub-slices toanother storage unit, wherein the other storage unit is the secondstorage unit or a different one of the storage units.
 8. A method forexecution by one or more processing modules of a storage unit of adispersed storage network (DSN), the method comprises: receiving anencoded data slice of a set of encoded data slices for storage, whereina data segment of data is dispersed storage error encoded into the setof encoded data slices; determining whether to store the encoded dataslice as the encoded data slice or as a set of encoded data sub-slices;when the encoded data slice is to be stored as the set of encoded datasub-slices, encoding the encoded data slice in accordance with adispersed storage error encoding function to produce the set of encodeddata sub-slices; determining whether to store an encoded data sub-sliceof the set of encoded data sub-slices in a memory device of anotherstorage unit; when the encoded data sub-slice is to be stored in thememory device of the other storage unit, sending the encoded datasub-slice to the other storage unit; determining a desired redundancylevel; and when the desired redundancy level is based on assurancesagainst memory device failure with the storage unit, determining thedispersed storage error encoding function based on the desiredredundancy level, wherein the dispersed storage error encoding functionincludes a pillar width number of n, a decode threshold number of k, andwhere n−k is less than n/2.
 9. The method of claim 8 further comprises:when the encoded data slice is to be stored as the encoded data slice,selecting a memory device of the storage unit; and storing the encodeddata slice in the selected memory device.
 10. The method of claim 8further comprises: storing remaining encoded data sub-slices of the setof encoded data sub-slices in a set of memory devices of the storageunit.
 11. The method of claim 8 further comprises: when the encoded datasub-slice is not to be stored in the memory device of the other storageunit, storing the set of encoded data sub-slices in a set of memorydevices of the storage unit.
 12. A non-transitory computer readablestorage medium comprises: at least one memory section that storesoperational instructions that, when executed by one or more processingmodules of one or more computing devices of a dispersed storage network(DSN), causes the one or more computing devices to: receive, by storageunits of the DSN, a set of encoded data slices for storage, wherein adata segment of data is dispersed storage error encoded into the set ofencoded data slices; determine, by a first storage unit of the storageunits, whether to store a first encoded data slice of the set of encodeddata slices as the first encoded data slice or as a first set of encodeddata sub-slices; when the first encoded data slice is to be stored asthe first set of encoded data sub-slices, encode, by the first storageunit, the first encoded data slice in accordance with a first dispersedstorage error encoding function to produce the first set of encoded datasub-slices; determine, by a second storage unit of the storage units,whether to store a second encoded data slice of the set of encoded dataslices as the second encoded data slice or as a second set of encodeddata sub-slices; and when the second encoded data slice is to be storedas the second set of encoded data sub-slices, encode, by the secondstorage unit, the second encoded data slice in accordance with a seconddispersed storage error encoding function to produce the second set ofencoded data sub-slices.
 13. The non-transitory computer readablestorage medium of claim 12 further comprises: the at least one memorysection stores further operational instructs that, when executed by theone or more processing modules, causes the one or more computing devicesof the DSN to: identify, by the first storage unit, a first set ofmemory devices within the first storage unit; store, by the firststorage unit, the first set of encoded data sub-slices in the first setof memory devices; identify, by the second storage unit, a second set ofmemory devices within the second storage unit; and store, by the secondstorage unit, the second set of encoded data sub-slices in the secondset of memory devices.
 14. The non-transitory computer readable storagemedium of claim 12 further comprises: the at least one memory sectionstores further operational instructs that, when executed by the one ormore processing modules, causes the one or more computing devices of theDSN to: determine, by the first storage unit, to store an encoded datasub-slice of the first set of encoded data sub-slices in a memory deviceof another storage unit of the storage units, wherein the other storageunit is the second storage unit or a different one of the storage units;send, by the first storage unit, the encoded data sub-slice to the otherstorage unit; and store, by the first storage unit, remaining encodeddata sub-slices of the first set of encoded data sub-slices in a set ofmemory devices within the first storage unit.
 15. The non-transitorycomputer readable storage medium of claim 14 further comprises: the atleast one memory section stores further operational instructs that, whenexecuted by the one or more processing modules, causes the one or morecomputing devices of the DSN to: select the other storage unit based onone or more selection criteria from a list of selection criteria,wherein the list of selection criteria includes: a query and responsewith the other storage unit; a pre-established relationship; an ad hocestablished relationship; and a determination that the other storageunit has a sufficient amount of available memory.
 16. The non-transitorycomputer readable storage medium of claim 14 further comprises: the atleast one memory section stores further operational instructs that, whenexecuted by the one or more processing modules, causes the one or morecomputing devices of the DSN to: determine to the store the encoded datasub-slice in the other storage unit based on one or more determinationcriteria from a list of determination criteria, wherein the list ofdetermination criteria includes: determining that the first storage unithas less than a desired amount of available memory; determining that thefirst storage unit has more than a desired number of memory device withan age issue; and determining that the other storage unit has moreavailable storage than the first storage unit.
 17. The non-transitorycomputer readable storage medium of claim 12 further comprises: the atleast one memory section stores further operational instructs that, whenexecuted by the one or more processing modules, causes the one or morecomputing devices of the DSN to: determine, by the first storage unit, adesired redundancy level; and when the desired redundancy level is basedon assurances against memory device failure with the first storage unit,determine, by the first storage unit, the first dispersed storage errorencoding function based on the desired redundancy level, wherein thefirst dispersed storage error encoding function includes a pillar widthnumber of n, a decode threshold number of k, and where n−k is less thann/2.
 18. The non-transitory computer readable storage medium of claim 12further comprises: the at least one memory section stores furtheroperational instructions that, when executed by the one or moreprocessing modules, causes the one or more computing devices of the DSNto: determine, by the first storage unit, a desired redundancy level;when the desired redundancy level is based on assurances against failureof the first storage unit, determine, by the first storage unit, thefirst dispersed storage error encoding function based on the desiredredundancy level, wherein the first dispersed storage error encodingfunction includes a pillar width number of n, a decode threshold numberof k, and where n−k is equal to or greater than n/2; and send, by thefirst storage unit, at least n/2 encoded data sub-slices of the firstset of encoded data sub-slices to another storage unit, wherein theother storage unit is the second storage unit or a different one of thestorage units.
 19. A storage unit of a dispersed storage network (DSN),the storage unit comprises: an interface; and a processing moduleoperably coupled to the interface, wherein the processing module isoperable to: receive an encoded data slice of a set of encoded dataslices for storage, wherein a data segment of data is dispersed storageerror encoded into the set of encoded data slices; determine whether tostore the encoded data slice as the encoded data slice or as a set ofencoded data sub-slices; when the encoded data slice is to be stored asthe set of encoded data sub-slices, encode the encoded data slice inaccordance with a dispersed storage error encoding function to producethe set of encoded data sub-slices; determine whether to store anencoded data sub-slice of the set of encoded data sub-slices in a memorydevice of another storage unit; when the encoded data sub-slice is to bestored in the memory device of the other storage unit, send the encodeddata sub-slice to the other storage unit; determine a desired redundancylevel; and when the desired redundancy level is based on assurancesagainst memory device failure with the storage unit, determine thedispersed storage error encoding function based on the desiredredundancy level, wherein the dispersed storage error encoding functionincludes a pillar width number of n, a decode threshold number of k, andwhere n−k is less than n/2.
 20. The storage unit of claim 19 furthercomprises: the processing module is further operable to: when theencoded data slice is to be stored as the encoded data slice, select amemory device of the storage unit; and store the encoded data slice inthe selected memory device.
 21. The storage unit of claim 19 furthercomprises: the processing module is further operable to: store remainingencoded data sub-slices of the set of encoded data sub-slices in a setof memory devices of the storage unit.
 22. The storage unit of claim 19further comprises: the processing module is further operable to: whenthe encoded data sub-slice is not to be stored in the memory device ofthe other storage unit, store the set of encoded data sub-slices in aset of memory devices of the storage unit.